Manifold Temperature Research Articles

Elucidating Optimal Exhaust Manifold Divergence and Temperature Distribution in Improving Low-End Engine Speed Performance

The exhaust manifold plays a crucial role in optimizing the performance of Spark-Ignition (SI) engines by effectively expelling combustion products. This study focuses on the optimization of the exhaust manifold design and temperature distribution in a 115-cc single-cylinder SI engine. The objective is to investigate the association between the design characteristics of the exhaust manifold, particularly its divergence, and the engine's performance in terms of brake power. Using computer-aided design (CAD), a three-dimensional model of the exhaust manifold with reduced diameter was developed. The optimized design aimed to enhance the engine's overall performance by achieving lower temperatures, particularly at low-end speeds. Subsequently, a 1D engine study was conducted to evaluate the performance of the engine with the optimized exhaust manifold design and validate the improved temperature distribution. The results demonstrate that the optimized exhaust manifold design leads to higher brake power while maintaining lower temperatures, especially at low-end speeds. This highlights the importance of exhaust manifold optimization and temperature distribution in maximizing the efficiency of the selected SI engine. To further enhance the engine's performance, future research should focus on identifying the most appropriate value for the exhaust manifold's divergence. This will contribute to the ongoing development of more efficient and high-performance SI engines. The findings of this study provide valuable insights into the optimization of exhaust manifold design and temperature distribution for improved engine performance in the context of the tested engine.

1-D ENGINE MODELING OF 4-CYLINDER TURBOCHARGED GASOLINE ENGINE

This project is conducted to explore one-dimensional (1D) simulation for a 4-cylinder gasoline engine. The simulation and computational development of modeling for the study are conducted by using the commercial Computational Fluid Dynamics (CFD) of AVL BOOST software. The engine model was developed corresponding to a Proton 1.6-litre CamPro 4-cylinder turbocharged gasoline engine including the real engine geometry and parameters. The engine model is based on 1D equation of the gas exchange process, progressive engine combustion process, isentropic compression and expansion, and accounting for the heat transfer as well as the frictional losses. The aim of the study is to predict the steady-state performance of the engine model at full and partload conditions from 1000 to 5000 rpm by using engine cycle simulation. In this study, three parameter tuning works have been performed, which are combustion model tuning, intake manifold temperature tuning and turbocharger’s scaling factor tuning. In addition, the comparison and validation were done for the output performance parameters based on the provided experimental data. Overall, the engine performance behavior have been observed to determine how accurate AVL BOOST software can evaluate engine performance compare to experiment conducted on the real engine. The most accurate validation of the engine performance parameters have been achieved by manifold absolute pressure (MAP) with 3.14% error. However, by comparing with experimental data, major discrepancy is noticeable on several engine performance parameters. From this study, the results showed that the engine model is able to simulate engine’s combustion process and produce reasonable prediction.

Parametric evaluation of ducted fuel injection in an optically accessible mixing-controlled compression-ignition engine with two- and four-duct assemblies

Ducted fuel injection (DFI) is a strategy to improve fuel/charge-gas mixing in direct-injection compression-ignition engines. DFI involves injecting fuel along the axis of a small tube in the combustion chamber, which promotes the formation of locally leaner mixtures in the autoignition zone relative to conventional diesel combustion. Previous work has demonstrated that DFI is effective at curtailing engine-out soot emissions across a wide range of operating conditions. This study extends previous investigations, presenting engine-out emissions and efficiency trends between ducted two-orifice and ducted four-orifice injector tip configurations. For each configuration, parameters investigated include injection pressure, injection duration, intake manifold pressure, intake manifold temperature, start of combustion timing, and intake-oxygen mole fraction. For both configurations and across all parameters, DFI reduced engine-out soot emissions compared to conventional diesel combustion, with little effect on other emissions and engine efficiency. Emissions trends for both configurations were qualitatively the same across the parameters investigated. The four-duct configuration had higher thermal efficiency and indicated-specific engine-out nitrogen oxide emissions but lower indicated-specific engine-out hydrocarbon and carbon monoxide emissions than the two-duct assembly. Both configurations achieved indicated-specific engine-out emissions for both soot and nitrogen oxides that comply with current on- and off-road heavy-duty regulations in the United States without exhaust-gas aftertreatment at an intake-oxygen mole fraction of 12%. High-speed in-cylinder imaging of natural soot luminosity shows that some conditions include a second soot-production phase late in the cycle. The probability of these late-cycle events is sensitive to both the number of ducted sprays and the operating conditions.

Combustion timing control of HCCI engine based on NNPC and Elman‐NN model under complex conditions

AbstractHomogeneous Charge Compression Ignition (HCCI) combines the characteristics of gasoline engine and diesel engine with high thermal efficiency and low emissions. However, since there is no direct initiator of combustion, it is difficult to control the combustion timing in HCCI engines under complex working conditions. In this paper, Neural Network Predictive Control (NNPC) for combustion timing of the HCCI engine is designed and implemented. First, the black box model based on Elman neural network is designed and developed to estimate the combustion timing. The fuel equivalence ratio, intake valve closing timing, intake manifold temperature, intake manifold gas pressure, and engine speed are chosen as the system inputs. Then, a NNPC controller is designed to control combustion timing by controlling the intake valve closing timing. Simulation results show that the Elman neural network black box model is capable of estimating the HCCI engine combustion timing. In addition, regardless of whether the HCCI engine is in constant or complex condition, the designed NNPC controller is capable of keeping the combustion timing within the ideal range. In particular, under New European Driving Cycle (NEDC) working conditions, the maximum overshoot of the controller is 28.95% and the average error is 1.03 crank angle degree. It is concluded that the controller has good adaptability and robustness.

Data-Driven Air-Fuel Path Control Design for Robust RCCI Engine Operation

Reactivity controlled compression ignition (RCCI) is a highly efficient and clean combustion concept, which enables the use of a wide range of renewable fuels. Consequently, this promising dual fuel combustion concept is of great interest for realizing climate neutral future transport. RCCI is very sensitive for operating conditions and requires advanced control strategies to guarantee stable and safe operation. For real-world RCCI implementation, we face control challenges related to transients and varying ambient conditions. Currently, a multivariable air–fuel path controller that can guarantee robust RCCI engine operation is lacking. In this work, we present a RCCI engine controller, which combines static decoupling and a diagonal MIMO feedback controller. For control design, a frequency domain-based approach is presented, which explicitly deals with cylinder-to-cylinder variations using data-driven, cylinder-individual combustion models. This approach enables a systematic trade-off between fast and robust performance and gives clear design criteria for stable operation. The performance of the developed multivariable engine controller is demonstrated on a six-cylinder diesel-E85 RCCI engine. From experimental results, it is concluded that the RCCI engine controller accurately tracks the five desired combustion and air path parameters, simultaneously. For the studied transient cycle, this results in 12.8% reduction in NOx emissions and peak in-cylinder pressure rise rates are reduced by 3.8 bar/deg CA. Compared to open-loop control, the stable and safe operating range is increased from 25 °C up to 35 °C intake manifold temperature and maximal load range is increased by 14.7% up to BMEP = 14.8 bar.

Study of NOx emission for hydrogen enriched compressed natural along with exhaust gas recirculation in spark ignition engine by Zeldovich’ mechanism, support vector machine and regression correlation

The hydrogen fuel is an ideal fuel to achieve the zero-carbon emission for heavy-duty vehicles. The experiments have been conducted under a wide range of operating conditions at different ignition timings (0 to 60°CA bTDC), hydrogen fractions (0–40%) in CNG fuel, EGR ratios (0–35.8%), manifold absolute pressures (65–178 kPa), engine speed (700–2000 rpm) at stoichiometric condition. The calibrated quasi-dimensional combustion model has been applied for simulation of in-cylinder pressure and temperature of HCNG engine. These combustion parameters have been utilized in Zeldovich’ mechanism for the prediction of NOx emission. The mean absolute percentage error is 69.1573% and R2 = 0.8353 that is quite high. The support vector machine and regression correlation have been applied for NOx modelling of HCNG engine.The four sets have been formulated at different independent variables: controllable parameters (engine speed, load, ignition timing, EGR ratio and hydrogen fraction in CNG fuel), combustion parameters (maximum pressure, indicated mean effective pressure, coefficient of variation and combustion duration), working medium parameters (inlet temperature, exhaust temperature, manifold absolute pressure and temperature of the coolant) and mixed parameters. The different sets of brake specific NOx emission have been trained by support vector machine algorithm at different independent variables, combinations (5C2, 5C3, 5C4, 5C5), tuning parameters (penalty factor kernel, function width & intensive band loss function) and sample sizes (decrement & increment of sample sizes). The minimum MAPE for SVM is 4.7490% & R2 = 0.9981. The mathematical modelling has been carried out with utilization of suitable independent parameters, combination and sample size. The mean absolute percentage error for regression correlation is 18.2461% and R2 = 0.9619.

Analysis of operating parameters of the aircraft piston engine in real operating conditions

The article presents the results of analysis of operational parameters of piston engine CA 912 ULT which is a propulsion system of ultralight gyroplane Tercel produced by Aviation Artur Trendak. Research was conducted under normal operating conditions of the autogyro and data was collected from 20 independent tests including a total of 28 flight hours, divided into training flights and competition flights.Engine speed, manifold air pressure and temperature, fuel pressure, injection time, and head temperature were recorded at 9 Hz during each flight. Collective results were presented to show the statistical analyses of the individual parameters by determining the mean values, standard deviations and histograms of the distribution of these parameters. Histograms of operating points defined by both engine speed and manifold air pressure were also determined. Analyses of the engine dynamics as a distribution of the rate of change of the engine rotational speed were also carried out. It was shown that the engine operating points are concentrated mainly in the range of idle and power above 50% of nominal power. The most frequent range is 70-80% of nominal power. It was also shown that the dynamics of engine work in real operating conditions is small. It was also shown that the way of use significantly influences the distribution of operating points. During training flights, an increase in the number of take-offs and landings causes an increase in the amount of engine work at take-off and nominal power and at idle.

Experimental and modeling analysis on the optimization of combined VVT and EGR strategies in turbocharged direct-injection gasoline engines with VNT

The combination of a growing number of complex technologies in internal combustion engines (ICE) is commonplace, due to the need of complying with the tight pollutant regulations and achieving high efficiencies. Hence the work of calibration engineers is led by a constant increase in degrees of freedom in ICE design. In this research work, a wide analysis on the optimization of combined variable valve timing (VVT) and exhaust gases recirculation (EGR) strategies is developed, in order to reduce fuel consumption in a EURO 6 1.3l 4-stroke 4-cylinder, gasoline, turbocharged, direct-injection engine, also equipped with a variable nozzle turbine (VNT). For that purpose, a methodology which combines 1D engine simulations with limited experimental work was applied. First, the data from 25 experimental tests distributed into three steady engine operating conditions was used to calibrate a 1D model. Then, modeling parametric studies were performed to optimize VVT and EGR parameters. A total of 150 cases were simulated for each operating point, in which VVT settings and EGR rate were varied at iso-air mass flow and iso-intake manifold temperature. The optimization was based on finding the configuration of VVT and EGR systems which maximizes the indicated efficiency. All different cases modeled were also evaluated in terms of pumping and heat losses. Moreover, a deep assessment of instantaneous pressure traces and mass flows in intake and exhaust valves was given, to provide insights about the optimization procedure. Finally, the findings obtained by simulation were compared with the results from a design of experiments (DOE) composed of more than 300 tests, and the impact on engine fuel consumption was analyzed.

Response surface method optimization of a natural gas engine with dedicated exhaust gas recirculation

Stoichiometric industrial natural gas engines rely on robust design to achieve consumer driven up-time requirements. Key to this design are exhaust components that are able to withstand high combustion temperatures found in this type of natural gas engine. The issue of exhaust component durability can be addressed by making improvements to materials and coatings or decreasing combustion temperatures. Among natural gas engine technologies shown to reduce combustion temperature, dedicated exhaust gas recirculation (EGR) has limited published research. However, due to the high nominal EGR rate it may be a technology useful for decreasing combustion temperature. In previous work by the author, dedicated EGR was implemented on a Caterpillar G3304 stoichiometric natural gas engine. Examination of combustion statistics showed that, in comparison to a conventional stoichiometric natural gas engine, operating with dedicated EGR requires adjustments to the combustion recipe to achieve acceptable engine operation. This work focuses on modifications to the combustion recipe necessary to improve combustion statistics such as coefficient of variance of indicated mean effective pressure (COV of IMEP), cylinder-cylinder indicated mean effective pressure (IMEP), location of 50% mass fraction burned, and 10%–90% mass fraction burn duration. Several engine operating variables were identified to affect these combustion statistics. A response surface method (RSM) optimization was chosen to find engine operating conditions that would result in improved combustion statistics. A third order factorial RSM optimization was sufficient for finding optimized operating conditions at 3.4 bar brake mean effective pressure (BMEP). The results showed that in an engine with a low turbulence combustion chamber, such as a G3304, optimized combustion statistics resulted from a dedicated cylinder lambda of 0.936, spark timing of 45° before top dead center (°bTDC), spark duration of 365 µs, and intake manifold temperature of 62°C. These operating conditions reduced dedicated cylinder COV of IMEP by 10% (absolute) and the difference between average stoichiometric cylinder and dedicated cylinder IMEP to 0.19 bar.

Throttle Control using NMPC with Soft Intake Temperature Constraint for Knock Mitigation

Abstract Knocking is an unwanted behavior that is affected by the intake manifold temperature. This paper demonstrates through simulation how nonlinear Model Predictive Control design could be used as a reference governor for the control of the throttle position, with a soft constraint on intake manifold temperature. The implementation is able to suppress the peak temperature during an acceleration by slowing down the pressure build-up. Because of the usually slow dynamics of the temperature sensors, the paper proposes an Extended Kalman Filter implementation that uses a transient detection to decide whether to rely on the sensor feedback or the model.

Study on Altitude Adaptability of a Turbocharged Off-Road Diesel Engine

Abstract This paper investigates the operating characteristics of an off-road diesel engine to enhance its power performance in plateau. First, the impacts of altitude on the power, fuel economy, and emissions characteristics were analyzed by a bench test. Second, the combustion and overall performance working at different altitudes were studied by three-dimensional numerical simulation, including the relationship between fuel injection parameters and engine performance. The results showed that altitude significantly affects the performance of the off-road diesel engine. As the altitude increased from 0 m to 2000 m, the engine power decreased as much as 4.3%, and the brake-specific fuel consumption (BSFC) increased as much as 6%. At the peak torque condition, the intake manifold boost pressure and the exhaust manifold pressure both reduced with a rise of altitude, while the intake and exhaust manifold temperatures both increased with a rise of altitude. Finally, after comparing the in-cylinder flow conditions and combustion characteristics given by six combustion chamber designs that have different shrinkage ratios, the engine performance at 4000 m altitude with five different fuel spray angles were further optimized. The engine rated power increased by 8.2% when the shrinkage ratio was 7.28% and the fuel spray angle was 150 deg at the 4000 m altitude.

Knock Mitigation Effectiveness of EGR across the Pressure-Temperature Domain

<div class="section abstract"><div class="htmlview paragraph">Exhaust gas recirculation (EGR) has been shown to enable efficiency improvements in SI engines through multiple different mechanisms, including decreasing the knock propensity at high load, which allows higher compression ratio. While many of the benefits of EGR are applicable to both low and high power density engines, including reductions in pumping work and improved specific heat ratio, the knock benefits and corresponding compression ratio increases have been limited to low power density naturally aspirated engines primarily intended for hybrid vehicle architectures. An earlier study [<span class="xref">1</span>] indicated that there may be a kinetic limitation for the ability of EGR to mitigate knock under these conditions, but that study only considered a small number of conditions. This investigation expands on that study while also providing data for model validation for the new light-duty combustion consortium from the U.S. Department of Energy: Partnership for Advancing Combustion Engines (PACE). In this investigation, the effectiveness of EGR to mitigate knock is studied with regards to the effect of engine speed (1,500 and 3,000 rpm), changing trajectory in the pressure-temperature domain by varying the intake manifold temperature (35, 60, and 90 deg C), and by considering the effect of minor species by studying the effect of untreated EGR vs. EGR that has been treated by an automotive three-way catalyst. Additionally, to increase the relevance of these data for future modeling studies, the performance of the full boiling range gasoline was compared relative to a surrogate formulation. The study found that the fuel surrogate performs well, confirmed the kinetic limitations of EGR to mitigate knock under boost, and showed improvements in EGR performance with catalyzed EGR.</div></div>

Investigating the effect of the air inlet temperature on the combustion characteristics of a spark ignition engine fueled by biogas

AbstractThis work has conducted a numerical study using AVL‐Boost engine simulation utilizing biogas (CH4 and CO2)–air mixtures in a SI engine model. The effect of varying the air manifold temperature from 25 to 50°C on the combustion characteristics as well as engine performance under full load condition in a SI engine fueled by gasoline and biogas mixtures has been investigated. The performed tests involved using variable concentrations of CO2 from 10% to 40% by volume. The current model has been validated with experimental results and it was found that the error in predicting the P‐θ behavior of the engine is about 4.89%. The results showed that, as the air inlet temperature increases, the volumetric efficiency decreases and the brake specific fuel consumption (BSFC) increases for gasoline and all biogas compositions. However, the peak pressure, brake output power, maximum pressure rise rate, and maximum heat release rate were decreased slightly with the increase in air inlet temperature. The effect was only observed for gasoline and the 10%‐CO2 biogas, whereas the effect on the maximum heat release rate was detected on gasoline and biogas compositions up to 20%‐CO2 only. On the other hand, the existence and growth of CO2 content in the biogas reduced significantly the peak pressure, brake output power, maximum pressure rise rate, volumetric efficiency, and both net and maximum heat release rates, though its effect in reducing the volumetric efficiency stopped at 20%‐CO2 biogas. Furthermore, BSFC rises noticeably with the increase in CO2 ratio in biogas. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

Effects of ethanol addition to biodiesel fuels derived from cottonseed oil and its cooking waste as fuel in a generator diesel engine

ABSTRACTExploration of energy sources such as renewable and non-edible vegetable oils has been continued during the recent two decades of 2000s. Cottonseed oil is a non-edible, abundant oil and is generally used as cooking oil. In the present study, the usability of biodiesel derived from both cottonseed oil and its cooking wastes was investigated by blending them with ULSD or ethanol in 50 percentages. B50, WB50, B50E50 and WB50E50, biodiesel and ethanol-contained fuels and ULSD were prepared for experiments. Combustion, performance, and emissions tests were conducted on a diesel engine used for power-producing electrical generator. In the combustion tests, cylinder pressure, HRR, CHR, MGT, and MFB were analyzed while MFC, BSFC, exhaust manifold temperature, and thermal efficiency were obtained in the performance tests. In the emissions tests, CO, HC, and NOx emissions were measured and compared with the results of ULSD. Combustion and performance findings of ULSD contained biodiesel blends were found more similar to those of ULSD. The duration of combustion stage can clearly be seen to be narrowed for ethanol-contained blend because of the rabid combustion characteristics of ethanol. Besides, the peak of HRR was found 10% higher for B50E50 while it was found averagely 8% for WB50E50 blends. NOx emissions were found 48% lower averagely for ethanol contained biodiesel blends that it is the most important finding of ethanol using with biodiesel. Besides, HC emissions were also found about 75% for biodiesel contained diesel fuel blends.

Experimental study on improving performance and emission characteristics of used motorcycle fueled with ethanol by exhaust gas heating transfer system

Reduction of environmental pollution and fossil fuel dependence are two worldwide concerned problems. Many research projects have addressed many solutions for these issues, in which, the trend of using bio-fuel has been widely studied and applied. Ethanol, a kind of biofuel has been used on motorcycle engines, which use carburetor system, to replace conventional gasoline. Ethanol is characterized by a higher heat of vaporization value than gasoline, thus the reduction of the intake manifold temperature which effects engine performance especially at cold starting and idling conditions. In this study, a certain amount of exhaust gas was recirculated to heat the intake manifold, thereby increasing intake mixture temperature, to improve the combustion process of the engine, results in improvement of engine performances. In experiment, an exhaust gas heating transfer system was designed to recirculate a partial mass of exhaust gas to transfer heat energy to the intake manifold of the test motorcycle fueled with ethanol. The experimental results show that, with the exhaust gas heating transfer system, the specific fuel consumption of the test engine improve remarkably and some gaseous emissions tend to be reduced; in addition, hot starting ability of the test engine with the heating transfer system improves significantly compared to the case of without the system.

Construction equipment engine performance degradation due to environmental and operation factors in Latin America

PurposeThe purpose of this paper is to determine whether the altitude at which construction equipment operates affects or contributes to increased engine wear.Design/methodology/approachThe study includes the evaluation of two John Deere PowerTech Plus 6,068 Tier 3 diesel engines, the utilization of OSA3 oil analysis laboratory equipment to analyze oil samples, the employment of standard sampling scope and methods, and the analysis of key Engine Control Unit (ECU) data points (machine utilization, Diagnostic Trouble Codes (DTCs) and engine sensor data).FindingsAt 250 h of engine oil use, the engine operating at 3,657 meters above sea level (MASL) had considerably more wear than the engine operating at 416 MASL. The leading and earliest indicator of engine wear was a high level of iron particles in the engine oil, reaching abnormal levels at 218 h. The following engine oil contaminants were more prevalent in the engine operating at the higher altitude: potassium, glycol, water and soot. Furthermore, the engine operating at higher altitude also presented abnormal and critical levels of oil viscosity, Total Base Number and oxidation. When comparing the oil sample analysis with the engine ECU data, it was determined that engine idling is a contributor for soot accumulation in the engine operating at the higher altitude. The most prevalent DTCs were water in fuel, extreme low coolant levels and extreme high exhaust manifold temperature. The ECU operating data demonstrated that the higher altitude environment caused the engine to miss-fire and rail pressure was irregular.Practical implicationsMany of the mining operations and construction projects are accomplished at mid to high altitudes. This research provides a comparison of how construction equipment engines are affected by this type of environment (i.e. higher altitudes, cooler temperatures and lower atmospheric pressure). Consequently, service engineers can implement maintenance strategies to minimize internal engine wear for equipment operating at higher altitudes.Originality/valueThe main contribution of this paper will help construction equipment end-users, maintenance engineers and manufacturers to implement mitigation strategies to improve engine durability for countries with operating conditions similar to those described in this research.

Development of a Hierarchical Observer for Burned Gas Fraction in Inlet Manifold of a Turbocharged Diesel Engine

Altogether with extent of automotive role in today's life, governments are approving stringent laws to lower the permitted level of automotive emissions. An important specie of automotive engines emissions is NOx. Different methods are developed to decrease the level of NOx generation; one of which is exhaust gas recirculation (EGR). Since the performance of EGR is strictly depended on burned gas fraction (BGF) in inlet manifold, the precise control of BGF is of importance. Unfortunately, due to inlet manifold temperature, no economical sensor is available to measure the BGF; therefore, estimators are employed instead. In this paper, a stable observer is designed for estimation of air fraction in inlet manifold. The governing equations are in the form of linear parameter varying (LPV). Since the LPV parameters are not directly measured, a hierarchical estimator structure is developed. Lyapunov theory is employed to design the higher level estimator, while high gain estimators and open-loop estimators are developed for estimation of the lower level parameters. Experimental test results show that the higher level estimator is able to estimate the BGF with high accuracy in both transient and steady states. Furthermore, it is shown that BGF estimator is more sensitive to aspirated gas flow estimation rather than exhaust temperature and pressure.

Advanced Air Path Control in Diesel Engines Accounting for Variable Operational Conditions

In this paper, we develop an extended linear parameter-varying (LPV) model to design an LPV controller for air path system control in diesel engines. The objective is to use a widely used and accepted nonlinear diesel engine air path model, minimize simplifying assumptions on the model, and then design a model-based gain scheduling controller to work in a wide range of engine operating points. To that end, we transform the nonlinear model to linear parameter-varying form by defining state-dependent inputs and scheduling parameters. Some of the defined state-dependent scheduling parameters are synthetic in the sense that they are not obvious from the model and are created through algebraic operations. The control law we design is parameter-dependent and allows a large range of operating points to be considered. The robust performance of the controller (with respect to parametric uncertainties in the control design model) under variable operating points (depending on engine speed, fuel flow rate, and intake-exhaust manifold temperatures) is tested on simulations by tracking reference exhaust manifold pressure and compressor air mass flow signals. Finally, the performance of the designed extended LPV controller is compared to an H∞ controller and to an LPV controller from the existing literature to see its superior performance under variable operating points.

Extending Substitution Limits of a Diesel–Natural Gas Dual Fuel Engine

New drilling techniques have increased availability and decreased costs of oil and gas. The decreased costs have caused an increase in drilling activity. The well sites have a large power demand that is typically met by diesel engines for the drilling derrick, fracking pumps, and electrical power. Dual fuel retrofit kits are being increasingly used at well sites to reduce operating costs and the amount of fuel trucked in to the site. Natural gas (NG) is cheaper compared to diesel and can be delivered to the site by the pipeline limiting the disturbance to surrounding communities due to diesel truck loads. The purpose of this work is to examine the performance of a typical dual fuel retrofit kit commissioned for field operation on a 6.8 L tier II diesel engine. After the baseline commissioning, the mechanisms limiting further substitution were clearly identified as engine knock similar to end gas auto-ignition in spark-ignited engines and governor instability. Two methods are examined for their ability to increase substitution limits by adjusting the start of injection timing (SOI) and the intake air manifold temperature. Retarding the SOI is able to delay the onset of knock at high loads and therefore increase the substitution level by around 4% at full load. At high loads, lowering the air manifold temperature is able to increase the substitution levels by around 10%. Preheating the intake air was able to increase low load substitution levels by 10% as well.

A second law-based framework to identify high efficiency pathways in dual fuel low temperature combustion

While dual fuel low temperature combustion (LTC) has been studied before, a detailed second law analysis of dual fuel LTC is not yet available in the open literature. To address this gap, a previously validated, closed-cycle, multi-zone, simulation of diesel-natural gas dual fuel LTC was used to perform a second law analysis. For the present study, a 2.4-l single-cylinder research engine operating at a nominal load of 6bar BMEP and 1700rpm was used. Zone-wise thermodynamic irreversibilities as well as total cumulative entropy generated and lost available work over the closed cycle were quantified. Subsequently, two convenient second-law parameters were defined: (1) the “lost available indicated mean effective pressure” (LAIMEP), which can be interpreted as an engine-size-normalized measure of available work that is lost due to thermodynamic irreversibilities (analogous to the relationship between indicated mean effective pressure and indicated work); (2) fuel conversion irreversibility (FCI), which is defined as the ratio of lost available work to total fuel chemical energy input. Finally, parametric studies were performed to quantify the effects of diesel start of injection, intake manifold temperature, and intake boost pressure on LAIMEP and FCI. The results show that significant entropy generation occurred in the flame zone (52–61 percent) and the burned zone (31–39 percent) while packets account for less than 6 percent of the overall irreversibilities. Parametric studies showed LAIMEPs in the range of 645–768kPa and FCIs in the range of 32.8–39.2 percent at different engine operating conditions. Although the present study focused on dual fuel LTC, the conceptual definitions of LAIMEP and FCI are generally applicable for comparing the thermodynamic irreversibilities of IC engines of any size and operating on any combustion strategy.