Intake Manifold Absolute Pressure Research Articles

Experimental study on Miller cycle hydrogen-enriched ammonia engine by rich-burn strategy

In order to achieve climate goals as soon as possible, it is necessary to reshape the energy mix to replace fossil energy with carbon–neutral fuels as soon as possible. Ammonia is a good medium for energy storage, has a large industrial scale and a well-developed infrastructure. To address the problems of NOx emission and low exhaust energy of ammonia-hydrogen engines, this study proposes a rich burn strategy. Firstly, a commercial spark ignition (SI) internal combustion engine (ICE) was modified to achieve a dual fuel supply of ammonia and hydrogen. The engine was run at a steady state of 1500 rpm with the intake manifold absolute pressure (MAP) maintained at 60 kPa, and the ammonia and hydrogen supplies were adjusted to achieve different mixing ratios and excess air ratios. The experimental results showed that the rich burn strategy could significantly reduce the NOx emission and increase the exhaust temperature of the ammonia-hydrogen engine when the excess air coefficient was below 0.8. The rich burn strategy can appropriately increase the engine power output, but it has some influence on the brake thermal efficiency (BTE).

Numerical study of the firing, radicals and intermediates in the combustion process of a H2-assisted combustion DISI methanol engine

The firing, radicals and intermediates in the combustion process of a port-injection hydrogen (H2)-assisted combustion direct-injection spark-ignition (DISI) methanol engine were numerically simulated. The engine with port-injection H2 plus direct-injection methanol was tested at 1800 rpm with intake manifold absolute pressure of 68 kPa. AVL-Fire coupling the detailed methanol chemical kinetics modeling with 21 components and 84 elementary reactions was used to simulate in this study. The model calculation results agreed well with the experiments, and the average error is less than 3% and can guarantee other outcomes. The simulation results show that high added H2 ratio (RH2) has higher turbulent kinetic energy in the region closer to the combustion chamber wall. When RH2 is greater than 6%, the formation time of fire core is obviously shortened and the average flame propagation velocity is significantly increased. Increasing RH2, the generation speed and the peak value of H, O and OH radicals increase, and higher concentration of radicals accelerates the diffusion of combustion from the hot flame zone. OH radical is a key reactant, which always plays a decisive role in the process of methanol oxidation. Effect of added H2 on methanol oxidation reaction is reflected in accelerating the initial stage of combustion and ameliorating the intensity of reaction. The mass fractions of HCHO, HCO and CO, as the main intermediate products, all show a trend of increasing first and then decreasing with the crank angle (CA), and their peak values indicate the phase of the most violent reaction. The peak values of HCHO and HCO are all near the top dead center (TDC), which is consistent with the trend of H and OH radicals generation rate. The relationship between consumption rate of methanol and CA shows that the consumption rate of methanol at RH2 = 9% is the earliest and steepest, and most of methanol has been consumed by reaction before TDC. Added H2 accelerates the fire propagation, H2 dominates the process of radical formation and methanol chain reaction, the flame spread period is shortened rapidly, and the effect of added H2 to promote combustion is obvious.

Monitoring of hydrogen-fueled engine backfires using dual manifold absolute pressure sensors

The application of hydrogen in internal combustion engines (ICE) has attracted widespread attention. However, due to the low ignition energy, high flame propagation speed, and wide combustible range of hydrogen, it is easy to cause abnormal combustion phenomena such as backfire in the port fuel injected (PFI) hydrogen-fueled engine. When a backfire occurs, the combustible mixture burns in the intake, resulting in a decrease in the volumetric efficiency of the engine, which may cause it to misfire or shut down in severe cases. Fast and accurate detection of backfire events is essential to take targeted control measures. In this research, a backfire detection system based on dual intake manifold absolute pressure (MAP) sensors were designed, with two MAP sensors installed on the intake manifolds of the first and fourth cylinders, and four gas injectors were installed on the intake manifold to convert the gasoline ICE into a hydrogen-fueled ICE. During the experiment, the engine speed was stabilized at 1000 rpm, the throttle valve was fully opened, and the intake pressure was maintained at 100 kPa.The test results show that the system can accurately determine the location and intensity of backfire occurrence. This method provides a basis for precise control of backfiring. • Set up two MAP sensors to monitor the backfiring of the hydrogen ICE. • MAP sensors allow accurate monitoring of backfiring. • Need to optimize valve strategy and injection strategy for hydrogen ICE.

An Experimental Study on Combustion and Cycle-by-Cycle Variations of an N-Butanol Engine with Hydrogen Direct Injection under Lean Burn Conditions.

This study experimentally investigated the effects of hydrogen direct injection on combustion and the cycle-by-cycle variations in a spark ignition n-butanol engine under lean burn conditions. For this purpose, a spark ignition engine installed with a hydrogen and n-butanol dual fuel injection system was specially developed. Experiments were conducted at four excess air ratios, four hydrogen fractions(φ(𝐻2)) and pure n-butanol. Engine speed and intake manifold absolute pressure (MAP) were kept at 1500 r/min and 43 kPa, respectively. The results indicate that the θ0–10 and θ10–90 decreased gradually with the increase in hydrogen fraction. Additionally, the indicated mean effective pressure (IMEP), the peak cylinder pressure (Pmax) and the maximum rate of pressure rise ((dP/dφ)max) increased gradually, while their cycle-by-cycle variations decreased with the increase in hydrogen fraction. In addition, the correlation between the (dP/dφ)max and its corresponding crank angle became weak with the increase in the excess air coefficient (λ), which tends to be strongly correlated with the increase in hydrogen fraction. The coefficient of variation of the Pmax and the IMEP increased with the increase in λ, while they decreased obviously after blending in the hydrogen under lean burn conditions. Furthermore, when λ was 1.0, a 5% hydrogen fraction improved the cycle-by-cycle variations most significantly. While a larger hydrogen fraction is needed to achieve the excellent combustion characteristics under lean burn conditions, hydrogen direct injection can promote combustion process and is beneficial for enhancing stable combustion and reducing the cycle-by-cycle variations.

Study on combustion and emissions of a hydrous ethanol/gasoline dual fuel engine with combined injection

Hydrous ethanol has lower cost and energy consumption during the production process than anhydrous ethanol. Many researchers used hydrous ethanol instead of anhydrous ethanol to manufacture hydrous ethanol-gasoline. The water ratio in hydrous ethanol (ω) determines the energy consumption in the production process of ethanol. However, no one researched the effects of different ω on combustion and emissions of hydrous ethanol-gasoline. So, we prepared five kinds of ethanol with different ω (0, 5%, 10%, 15%, 20% vol.) to research the effects of ω on combustion and emissions. This study adopted combined injection with hydrous ethanol direct injection plus gasoline port injection (HEDI + GPI). The engine speed was 1500 rpm, and λ was 1, the intake manifold absolute pressure was 48 kPa, the direct injection ratio was 20%, five spark timings varied from 5 °CA BTDC to 25 °CA BTDC. The results showed hydrous ethanol prolonged flame development and propagation duration, decreased Tmax and Pmax, delayed APmax. Water increased COVimep, but using hydrous ethanol at the reasonable spark timing would not significantly affect the stability. Meanwhile, when the spark timing was MBT, compared with GE (gasoline/anhydrous ethanol dual fuel) fuel, as ω in GEW (gasoline/hydrous ethanol dual fuel) fuels increased, torque and brake thermal efficiency improved by 1.69%, 1.13%, −0.01%, −0.77%; HC increased by 2.13%, 9.02%, 23.89%, 37.15%; CO decreased by 41.95%, 28.56%, 5.59%, 2.46%; NOx decreased by 10.10%, −0.75%, −0.17%, 4.18%; total PN emissions decreased by 24.07%, 69.57%, 36.34%, 32.45%. Meanwhile, more water caused the size of particles to drop, made particles smaller.

Effects of Water Ratio in Hydrous Ethanol on the Combustion and Emissions of a Hydrous Ethanol/Gasoline Combined Injection Engine under Different Excess Air Ratios.

Ethanol is usually combined with gasoline to manufacture ethanol–gasoline with excellent combustion characteristics. However, extracting water from hydrous ethanol to manufacture anhydrous ethanol consumed much energy, which increases the production cost of ethanol–gasoline. Many researchers have studied the combustion and emissions of hydrous ethanol–gasoline to explore the application of hydrous ethanol–gasoline as the fuel for spark-ignition engines. Most previous studies changed the hydrous ethanol ratio with fixed purity in hydrous ethanol–gasoline to study the effects of hydrous ethanol. Different from previous studies, this paper studied the effects of water ratio (Wr) in hydrous ethanol on the combustion and emissions of a hydrous ethanol/gasoline combined injection engine under different excess air ratio (λ) values. The ratios of ethanol and gasoline keep constant, while the purity of hydrous ethanol changes during the research. The experiment adopted the combined injection mode with hydrous ethanol direct injection plus gasoline port injection; the direct injection ratio was 20%. The experiment set three λ (0.9, 1, and 1.2) and five Wrs (0, 5, 10, 15, and 20%). The test engine’s speed was 1500 rpm, and the intake manifold absolute pressure was 48 kPa. Results showed that water inhibited combustion, prolonged CA 0-10 and CA 10-90, reduced Pmax and Tmax, and delayed APmax; larger λ made the deterioration on combustion more obvious, and the smaller λ had a larger tolerance to water. Water could increase torque and improve emissions, but different parameters corresponded to different optimal Wrs. For torque, the optimal Wr was 5%. For HC emissions, the optimal Wr was 0%; for CO emissions, the optimal value was 5%; and for NOx emissions, the best value was 20%. The best Wr was 10% for particle number (PN) emissions. Under the optimal Wr condition, when λ values were 0.9, 1, and 1.2, compared with pure gasoline, the torque increased by 7.5, 5.54, and 5.31%; HC emissions decreased by 21.37, 23.43, and 26.58%; NOx emissions decreased by 4.26, 11.47, and 12.55%; CO emissions decreased by 17.51, 34.56, −50%; and the total PN emissions decreased by 87.64, 89.64, and 76.07%.

Influence of fuel injection strategies on efficiency and particulate emissions of gasoline and ethanol blends in a turbocharged multi-cylinder direct injection engine

The effects of a broad range of fuel injection strategies on thermal efficiency and engine-out emissions (CO, total hydrocarbons, NOx and particulate number) were studied for gasoline and ethanol fuel blends. A state-of-the-art production multi-cylinder turbocharged gasoline direct injection engine equipped with piezoelectric injectors was used to study fuels and fueling strategies not previously considered in the literature. A large parametric space was considered including up to four fuel injection events with variable injection timing and variable fuel mass in each injection event. Fuel blends of E30 (30% by volume ethanol) and E85 (85% by volume ethanol) were compared with baseline E0 (reference grade gasoline). The engine was operated over a range of loads with intake manifold absolute pressure from 800 to 1200 mbar. A combined application of ethanol blends with a multiple injection strategy yielded considerable improvement in engine-out particulate and gaseous emissions while maintaining or slightly improving engine brake thermal efficiency. The weighted injection spread parameter defined in this study, combined with the weighted center of injection timing defined in the previous literature, was found well suited to characterize multiple injection strategies, including the effects of the number of injections, fuel mass in each injection and the dwell time between injections.

EVALUATION METHODS AND WAYS OF IMPROVING THE OPERATIONAL DEPENDABILITY OF MASS AIRFLOW SENSORS IN ENGINES

The design of today’s car engine electronic control system practically always includes an engine load sensor. Normally, its role is played by the intake manifold absolute pressure sensor or the mass airflow sensor. Film mass airflow sensors are the most common ones. The sensor is installed in the intake between the air filter and the throttle plate of the engine intake manifold. In the process of operation the sensor is exposed to pollution and ageing of the gauging element due to interaction with dust particles and motor oil fumes in the airflow. That causes the output signal to deviate from the reference values and consequently inaccurate calculation of the fuel blend composition by the electronic engine control system. Given the design of the sensors, they cannot be repaired and are replaced with new ones. A new sensor is quite costly. Given the above, it is obvious that the subject is of relevance. The aim of the paper is to find methods of evaluation and ways of improving the operational dependability of film mass airflow sensors installed in modern automobiles. The evaluation of sensor operability is based on the voltage of the sensor output signal. Using a diagnostic scanner plugged into the automobile’s diagnostics port in the analog-to-digital converter channel viewing mode the voltage of the sensor output signal is recorded, the fuel blend long-lasting correction factor is evaluated, and the presence of error codes associated with the malfunction of mass airflow sensor in the memory of electronic control unit is verified. A digital oscilloscope is used for measuring the voltage at the moment of ignition lock activation and the resting voltage at zero airflow, as well as the transient time. Based on the obtained findings it becomes obvious that the operational dependability of such sensors can only be improved by correcting the calibration tables of the mass airflow sensor stored in the memory of the engine control unit. Using a mass airflow sensor test stand, input data is prepared for the correction procedure. The reference and tested sensors are installed on the same vacuum pump nozzle, and the airflow rate is changed gradually. Under a fixed airflow rate the sensors’ output voltage is measured. The resulting data is summarized in a table and processed with the Chip Tuning PRO calibration software. As can be seen, one of the causes of the loss of the sensors’ operational dependability is the pollution of the sensing element. The layer of pollution on the sensing element reduces the coefficient of heat transmission between the airflow and the sensor’s gauging element. Based on the conducted research, the paper presents the results of changing sensor output signal in operation as compared to the reference values, suggests a method of correction of the calibration table of mass airflow sensor parameters in the engine control program stored in the memory of the electronic control unit, provides recommendations regarding the methods of evaluation and ways of improving the sensors’ operational dependability.

Control of 12-Cylinder Camless Engine with Neural Networks

The 12-cyliner camless engine breathing process is modeled with artificial neural networks (ANN’s). The inputs to the net are the intake valve lift (IVL) and intake valve closing timing (IVC) whereas the output of the net is the cylinder air charge (CAC). The ANN is trained with data collected from an engine simulation model which is based on thermodynamics principles and calibrated against real engine data. A method for adapting single-output feed-forward neural networks is proposed and applied to the camless engine ANN model. As a consequence the overall 12-cyliner camless engine feedback controller is upgraded and the necessary changes are implemented in order to contain the adaptive neural network with the objective of tracking the cylinder air charge (driver’s torque demand) while minimizing the pumping losses (increasing engine efficiency). All the needed measurements are extracted only from the two conventional and inexpensive sensors, namely, the mass air flow through the throttle body (MAF) and the intake manifold absolute pressure (MAP) sensors. The feedback controller’s capability is demonstrated through computer simulation.

Experiments and Simulations of a Lean-Boost Spark Ignition Engine for Thermal Efficiency Improvement

<div class="section abstract"><div class="htmlview paragraph">Primary work is to investigate premixed laminar flame propagation in a constant volume chamber of iso-octane/air combustion. Experimental and numerical results are investigated by comparing flame front displacements under lean to rich conditions. As the laminar flame depends on equivalence ratio, temperature, and pressure conditions, it is a main property for chemical reaction mechanism validation. Firstly, one-dimensional laminar flame burning velocities are predicted in order to validate a reduced chemical reaction mechanism. A set of laminar burning velocities with pressure, temperature, and mixture equivalence ratio dependences are combined into a 3D-CFD calculation to compare the predicted flame front displacements with that of experiments. It is found that the reaction mechanism is well validated under the coupled 1D-3D combustion calculations. Next, lean experiments are operated in a SI engine by boosting intake pressure to maintain high efficiency without output power penalty. The peak indicated thermal efficiency are finally achieved under λ=1.3 with intake manifold absolute pressure 150 kPa in experiment. Data of in-cylinder pressure and rate of heat release from the 3D-CFD simulations combined with the validated chemical reaction mechanism are reproduced. NOx emissions from experiment and simulation are also in good agreements under the lean-boost combustion. Further thermal efficiency improvements of the lean-boost SI engine are investigated numerically by using dilution rate, high induced in-cylinder flow, and high knock resistant fuel. The peak indicated thermal efficiency and load of the SI engine is achieved. In addition, methods to prevent knock for high efficiency spark ignition engine are also discussed.</div></div>

TCC-III Engine Benchmark for Large-Eddy Simulation of IC Engine Flows

A collaborative effort is described to benchmark the TCC-III engine, and to illustrate the application of this data for the evaluation of sub-grid scale models and valve simulation details on the fidelity of Large-Eddy Simulations (LES). The TCC-III is a spark ignition 4-stroke 2-valve engine with a flat head and piston and is equipped with a full quartz liner for maximum optical access that allows high-speed flow measurements with Particle Image Velocimetry (PIV); the TCC-III has new valve seats and a modified intake-system compared to previous configurations. This work is an extension of a previous study at an engine speed of 800 RPM and an intake manifold pressure (MAP) of 95 kPa, where a one-equation eddy viscosity LES model yielded accurate qualitative and quantitative predictions of ensemble averaged mean and RMS velocities during the intake and compression stroke. Here, experimental data were acquired with parametric variation of engine speed and intake manifold absolute pressure to assess the capability of LES models over a range of operating conditions of practical relevance. This paper focuses on the repeatability and accuracy of the measured PIV data, acquired at 1 300 RPM, at two different MAP (95 kPa and 40 kPa), and imaged at multiple data planes and crank angles. Two examples are provided, illustrating the application of this data to LES model development. In one example, the experimental data are used to distinguish between the efficacies of a one-equation eddy viscosity model versus a dynamic structure one-equation model for the sub-grid stresses. The second example addresses the effects of numerical intake-valve opening strategy and local mesh refinement in the valve curtain.

Design and Development of OBD-II Compliant Driver Information System

Background/Objectives: On-Board Diagnostics, or OBD, in a vehicle connection, is a term alluding to a vehicle's logical toward oneself and reporting ability. OBD systems give the vehicle proprietor or a repair expert access to condition of origin data for different vehicle sub-systems. Methods/Statistical Analysis: The driver data framework (DIS) is connected in a vehicle through OBD-II connector. Initially, live information undertaking that gives real time gauges reading. The live information is constrained to show an ambient temperature, Throttle position, Intake manifold absolute pressure, MAF air flow rate, calculated engine load value, intake air temperature, Engine coolant temperature, RPM and vehicle speed (km/h). Second assignment is DTC filtering framework that offers diagnostic trouble codes. Findings: The point of this venture is to get a completely useful Programmable System on Chip (PSoC) platform working with observing live data monitoring and DTCs corresponds with all present day vehicles. Correspondence to and from the ECU will be done utilizing the On-Board Diagnostics two (OBD-II) standard. The correspondence with the ECU must be taken care of utilizing a surveying sort system as information programmed overhauling of information from the ECU isn't possible sporadically. Rather a cyclic process or string will need to run ceaselessly to do a question to the ECU took after by the perusing of the answer. The product will need to work with the returned hexadecimal information in a manner that gives the client or driver valuable information. Conclusion/Improvements: Driver Information System (DIS) helps effective and efficient use of vehicles and can assist a relatively inexperienced drive to shift to proper gears or proper acceleration according to the load on the engine and there by achieve better fuel economy and better emission performance.

Effects of Ethanol on In-Cylinder and Exhaust Gas Particulate Emissions of a Gasoline Direct Injection Spark Ignition Engine

The effects of ethanol on reducing the particulate emissions of a direct injection spark ignition (DISI) engine were investigated using a single-cylinder, optically accessible engine. Neat anhydrous ethanol was compared with a baseline fuel of reference grade gasoline. A high speed camera was used to record crank-angle resolved in-cylinder images of the fuel spray, combustion, and thermal radiation from the soot formed for the engine operating conditions studied. Particulate emissions in the engine exhaust gas were also measured using opacity measurements (i.e., using a smoke meter). All experiments were conducted at the same load conditions with a net indicated mean effective pressure of IMEPnet ≈ 5.5 bar and an intake manifold absolute pressure of 76 kPa. The engine speed was fixed at 1500 rpm, and the fuel injection duration was controlled to achieve stoichiometric combustion. Spark timing was adjusted to target combustion phasing (CA50) of 8° aTDC. The effects of engine coolant temperature and fuel injection timing on fuel spray characteristics and soot formation were studied for each fuel. The imaging data indicate that soot formation is a strong function of liquid fuel impingement on the piston surface, consistent with previous in-cylinder imaging studies of soot formation in DISI engines using different engine hardware and imaging orientation. A quantitative metric was applied to the imaging data of this work, and the in-cylinder soot formation based on the imaging data were in good agreement with the engine-out smoke measurements, indicating the optical imaging results are representative of engine-out particulate emissions. Higher coolant temperatures and later fuel injection timing significantly mitigated the in-cylinder soot emissions for both fuels by altering the fuel spray interactions with the piston surface and cylinder liner. As expected based on previous studies, ethanol systematically produced less soot than gasoline for each operating condition. Features of the fuel spray roll-up were identified as important indicators of pool fires on the piston surface for the earliest fuel injection timings.

AFR-Based Fuel Ethanol Content Estimation in Flex-Fuel Engines Tolerant to MAF Sensor Drifts

Flexible fuel vehicles (FFVs) can operate on a blend of ethanol and gasoline in any volumetric concentration of up to 85% ethanol (93% in Brazil). Existing FFVs rely on ethanol sensor installed in the vehicle fueling system, or on an ethanol estimation based on air-to-fuel ratio (AFR) regulation via an exhaust gas oxygen (EGO) or λ sensor. The EGO-based ethanol detection is desirable from cost and maintenance perspectives but it is known to be prone to large errors during mass air flow sensor drifts. Ethanol content estimation can be realized by a feedback-based fuel correction of the feedforward-based fuel calculation using an exhaust gas oxygen sensor. When the fuel correction is attributed to the difference in stoichiometric air-to-fuel ratio (SAFR) between ethanol and gasoline, it can be used for ethanol estimation. When the fuel correction is attributed to a mass air flow (MAF) sensor error, it can be used for sensor drift estimation and correction. Deciding under which condition to blame (and detect) ethanol and when to switch to sensor correction burdens the calibration of FFV engine controllers. Moreover, erroneous decisions can lead to biases in ethanol estimation and in MAF sensor correction. In this paper, we present AFR-based ethanol content estimation, associated sensitivity and dynamical analysis, and a cylinder air flow estimation scheme that accounts for MAF sensor drift or bias using an intake manifold absolute pressure (MAP) sensor. The proposed fusion of the MAF, MAP, and λ sensor measurements prevents severe misestimation of ethanol content in flex fuel vehicles.

Effects of Errors on Vehicle Emission Rates from Portable Emissions Measurement Systems

Portable emissions measurement systems (PEMS) are useful for quantification of real-world vehicle activity, energy use, and emissions. However, there is no standard methodology for processing PEMS data; this can lead to errors in reported results. PEMS typically include tailpipe exhaust gas and particle analyzers, Global Positioning System (GPS) receivers, engine sensors, and electronic control unit (ECU) data loggers. The sensitivity of estimated emission rates to random errors in measurements is quantified. Methods are evaluated for identification and correction of improper synchronization of PEMS, ECU, and GPS data streams and for road grade estimation. Estimated fuel use and emission rates for light- and heavy-duty vehicles are sensitive to errors in intake manifold absolute pressure and engine revolutions per minute values and in indicators of air-to-fuel ratio including carbon dioxide and oxygen concentrations. Synchronization can be aided by maximizing the Pearson correlation coefficient between two indicator variables and confirming the result by matching concurrent increases in indicator variables. The effect of improper synchronization on estimated modal emission rates is quantified. Modal average emission rates based on vehicle-specific power (VSP) are more sensitive to improperly synchronized engine versus GPS data. Improperly synchronized data streams result in decreased variability between the lowest and highest modal average emission rates. Estimation of road grade from a linear least squares slope of elevation over a specified distance is demonstrated. VSP-based modal fuel use and pollutant emission rates are less sensitive to differences in road grade than to errors in synchronization.

Investigation on the performance of a spark-ignited ethanol engine with DME enrichment

Dimethyl ether (DME) is thought to be one of the most favorable alternative fuels or additives for internal combustion (IC) engines in the future. Because spark-ignited (SI) ethanol engines have the poor performance at cold start and low operating conditions caused by negative properties of ethanol such as the high latent heat, DME is introduced aiming at improving the engine economical and emissions performance. The experiments were carried out on a modified 4-cylinder gasoline engine under a typical city driving speed of 1400rpm and an intake manifold absolute pressure (MAP) of 61.5kPa. In this paper, the effect of DME blending on the engine performance at different excess air ratios and two DME volume fractions of 1% and 2% was experimentally investigated. The engine manifold was modified so that ethanol and DME can be injected and mixed with air simultaneously in the intake ports. A hybrid electronic control unit (HECU) was specially developed to control the injection timings and durations of ethanol and DME, accomplishing specified excess air ratios and DME volume fractions in the intake. The experimental results indicated that, DME addition benefits enhancing the indicated thermal efficiency, which is increased by about 10% at λ=1.25 compared with the original ethanol engine. And the maximum reduction of COVimep is about 50% after DME addition. Besides, the HC emissions from the DME-enriched ethanol engine at the DME volume fraction of 2% are averagely reduced by 45% compared with those from the original ethanol engine. But the NOx emissions slightly increase with the increase of DME volume fraction in the intake. Consequently, DME addition can be considered as a potentially applicable approach for improving the overall performance of SI ethanol engines.

Transient characteristics of emissions during engine start/stop operation employing a conventional gasoline engine for HEV application

In this paper, we investigate the transient characteristics of combustion and emissions during engine start/stop operations in hybrid electric vehicle (HEV) applications. Hydrocarbon (HC) emissions during the initial 2nd∼9th cycles are found to be significantly greater when the engine is quickly started under the original engine calibration mode. Lower intake manifold absolute pressure (MAP) was also found to cause larger residual gas dilution and poor combustion, resulting in a higher HC concentration when the cranking speed was increased. The post-catalyst HC concentration was found in the way of initially decrease and then to increase again as the cranking speed was increased. A lowest concentration value was achieved at a cranking speed of 1000 r/min. Engine shut-down by fuel cut-off was shown to produce lower emissions than shut-down by ignition cut-off as one can avoid misfire of the last fuel injection cycle. The fuel deposited during the stop process seems to impact engine restart enrichment mostly during the initial 0.7 s for this engine, whose performance is dominated by the MAP transition characteristic and the time coefficient for fuel vaporization in this time period

Behavioral Circuit Macromodeling and Analog LSI Implementation for Automobile Engine Intake System

Accurate estimating or measuring the intake manifold absolute pressure plays an important role in automobile engine control. In order to achieve the real-time estimation of the absolute pressure, the high accuracy and high speed processing ability are required for automobile engine control systems. Therefore, in this paper, an analog method is discussed and a fully integrated analog circuit is proposed to simulate automobile intake systems. Furthermore, a novel behavioral macromodeling is proposed for the analog circuit design. With the analog circuit, the intake manifold absolute pressure, which plays an important role for the effective automobile engine control, can be accurately estimated or measured in real time.