Exhaust Temperature Research Articles

Study on Urea Crystallization Risk Assessment and Influencing Factors in After-Treatment System of Diesel Engines

In order to meet the increasing pollutants discharge standard, the selective catalytic reduction (SCR) module in the diesel engine after-treatment system is an important means to reduce nitrogen oxide (NOx) emissions. SCR systems are prone to urea crystallization at lower temperatures, especially during the cold-start conditions of diesel engines. In this study, we use the diesel engine after-treatment system test bench to obtain the boundary parameter of the simulation modules, and the urea crystallization risk assessment model of the diesel SCR system is established. Comparing the computational fluid dynamics (CFD) results with the test bench results, it is shown that the predicted urea film distribution of the assessment model is in good agreement with the experimental results. In order to clarify the various factors that affect the urea crystallization risk, this paper conducts a simulation analysis on a nozzle and mixer structure and operating parameters. The CFD results indicate that the increase in urea spray time will increase the maximum urea film thickness on the SCR system mixer surface. Exhaust temperature is the most important influencing factor. When the diesel engine exhaust temperature increases from 190 °C to 300 °C, the maximum urea film thickness decreases by 32 and the urea film mass accumulation decreases by 5%. Exhaust flow has a small impact on urea crystallization risk. When the exhaust flow increases from 300 kg/h to 600 kg/h, the maximum urea film thickness decreases by 39% and the urea film mass accumulation decreases by about 1%. In addition, urea spray rate, nozzle numbers, spray angle, and spray cone angle are also factors that affect urea crystallization risk.

Effect of Di-tert Butyl Peroxide on Diesel Engine Performance Fuelled by Biodiesel Blends

This study is motivated by the fact that the vegetable oils are being considered as the fuel of the future for the internal combustion engines, especially the compression ignition engines which are working with diesel as fuel. Different approaches for using the vegetable oils in CI engines as fuel are either to modify the oils to match with that of diesel to run successfully with these oils. Fuel additives are compounds formulated to enhance the quality and efficiency of the fuels used in motor vehicles. There are several benefits associated with the use of fuel additives. Di-tert butyl peroxide (DTBP) is effective for enhance the quality and efficiency of the fuels used in CI engine. The investigation was to check the feasibility of di-tert butyl peroxide as an additive in different blends of diesel and jetropha bio-diesel on engine performance. The short-term tests on an unmodified diesel engine were conducted using the bio diesel and di-tert butyl peroxide blends (0, 10, 20, 30, 40, 50, and 100 per cent and 0, 0.5, 1.0, 1.5, 2.0, 2.5 per cent) with diesel. The engine performance and emission characteristics were measured during the short-term test. In all types of fuel, with increased percentage of load, brake specific energy consumption (BSEC) of the engine was observed to be decreased, on the other hand brake thermal efficiency, fuel consumption rate, sound level (db.), exhaust temperature, and the engine exhaust emissions like CO2, CO, HC and NOx was increased, respectively.

Exploring the dynamic characteristics of thermoelectric generator under fluctuations of exhaust heat

The thermoelectric generator is a potential candidate to recover waste heat from exhaust gas. Regarding the fluctuations of exhaust heat in practical situations, this paper adopts a transient fluid-thermal-electric multiphysics model to investigate the dynamic performance of the thermoelectric generator. Results show that the fluctuation of exhaust temperature has a greater influence on the dynamic characteristics than the fluctuation of exhaust mass flow rate. The dynamic performance of the thermoelectric generator benefits from a decrease in exhaust heat, but suffers when the exhaust heat is in an upward trend. Compared with the constant power and efficiency values of 4.96 W and 2.49 %, the average power and efficiency of the thermoelectric generator show a notable increase of 5.50 % and 70.61 % respectively during a step decrease in exhaust mass flow rate. Similarly, under a linear decrease, the mean power and efficiency experience a rise of 6.04 % and 45.05 % respectively. Besides, periodic exhaust heat can effectively amplify the dynamic output performance, especially for conversion efficiency. When subjected to a sin wave of exhaust mass flow rate, the efficiency experiences a 15.58 % improvement. This work offers a comprehensive understanding of the dynamic characteristics exhibited by the thermoelectric generator employed for waste heat recovery.

Analysis of Gasoline Engine Exhaust Emissions Using a Hydrocarbon Crack System

The increase in the number of motorbikes as a means of transportation results in increased exhaust emissions resulting from combustion of gasoline engines and is dangerous for human health. The use of a Hydrocarbon Crack System is one solution to reduce exhaust emissions in gasoline engines. Hydrocarbon Crack System can perfect the combustion process resulting in low exhaust emissions. The aim of this research is knowing gasoline engine exhaust emissions using the Hydrocarbon Crack System. The research used experimental methods applied to gasoline engine motorbikes with a fuel injection system. Adding Hydrocarbon Crack System is a tool to break down hydrocarbon elements in fuel gas. The use of the Hydrocarbon Crack System in gasoline engines reduces the levels of HC 20 percent and CO 4 percent exhaust emissions at rpm 5500 and above and the exhaust temperature is 215 degrees celsius so that it can maximize the work of the catalyst.

Effect of Intake Conditions and Combustion Factors on Gasoline and Diesel Engines Performance and Exhaust Emissions

The study aimed to investigate the effects of intake conditions, including water injection, filter presence, and temperature variations, on the performance of petrol and diesel engines. The experiment was conducted on single-cylinder four-stroke engines at varying speeds and loads. The composition of the exhaust emissions was analyzed to determine the combustion method. The results indicated that injecting a mixture of water and air into the engine inlet could reduce engine emissions by 17-33% and exhaust temperature by 13-35% for both engines. When an air filter and water injection were present, air flow restrictions in the air inlet led to better combustion and less unburned mixture due to increased air availability. The study also investigated the impact of combustion parameters on heat generation and emissions inside the combustion chamber of gasoline and diesel engines. The parameters studied included intake temperature, intake pressure, equivalence ratio, compression ratio, engine speed, turbulence kinetic energy, and combustion chamber design. The test results showed that higher intake temperatures lead to increased heat generation, increased overall engine efficiency, and reduced CO2 and NOx emissions in gasoline engines. Increasing the value of the parity ratio also led to improved overall efficiency of the two engines.

Thermoeconomic simulation of a complex energy system for performance analysis and prediction in deep peak shaving

The establishment of a cost model for complex energy systems based on thermoeconomics can provide technical and economic evaluation indicators for complex energy systems. At the same time, to integrate more renewable energy into the grid, complex energy systems must participate in deep peak shaving. To evaluate the technical-economic performance of complex energy systems involved in deep peak shaving, a novel thermoeconomic cost construction method is proposed based on the production structure diagram, using the gas-steam combined cycle system as an example. these can effectively avoid the derivation error of high-dimensional models, improve the modeling and calculation speed, and obtain the variation trend of system thermoeconomics cost under load changes and operating parameter changes. The results show that the external and internal factor can change the power generator thermoeconomic cost. the power generation cost of the system increases with increasing natural gas price and environmental temperature When the compressor pressure ratio increases, the power generation cost of the system also increases. At 100% load, the power generation cost reaches its lowest value when the exhaust temperature is equal to 615?C.

Experimental study on refrigeration system’s performance of the refrigerator truck using R404A refrigerant

A refrigerated system experimental bench using R404A as the refrigerant was built to address the current issues of high compressor discharge temperature and poor refrigeration performance of refrigerated systems for cold storage. The effects of compressor speed and temperature changes within the storage on the main refrigeration performance parameters of the system were studied and analyzed. The results show that when the rotational speed is increased from 2500-4500 rpm under the conditions of 32?C outside and 0?C inside, the highest system exhaust temperature is 84.3?C, which is lower than 90?C, and the maximum system COP is 3.86, and when the compressor speed is increased from 3500 rpm under the conditions of -5?C to 5?C, the system exhaust temperature is lower than 90?C. The COP can reach 2.74, especially at -5?C.

Effect of superheat on refrigeration system performance of refrigerated truck

According to the characteristics of variable operating conditions and high exhaust temperature of the refrigeration system of the refrigerator truck, the change of the superheat at the outlet of the evaporator is adjusted by a new electronic expansion valve, and a performance test-bed using the R404A refrigerant is built to study the influence of the superheat at the outlet of the evaporator on the performance of the refrigeration system of the refrigerator truck. The results show that in the process of increasing the superheat at the outlet of the evaporator, the outlet temperature of the evaporator increases and the evaporation temperature decrease, the cooling capacity of the system is reduced by 8.4%, and the COP of the system increases first and then decreases; At this time, the optimal superheat at the evaporator outlet is 6?C, and the system COP reaches the optimal value of 2.856.

Research on combustion visualization of coal-fired boilers based on thermal imaging technology

At present, there?s a lack of combustion visualization in the combustion control of heating boilers. To understand the combustion of coal in the furnace, only experienced workers can observe it through visual inspection. Using infrared thermal imaging technology to monitor the combustion can realize combustion visualization. This paper analyzed and solved two problems: the installation position and number of infrared cameras, and the infeasible of using infrared cameras observing the combustion condition in the furnace through heat-resistant glass. Monitored parameters such as oxygen content, furnace temperature and smoke exhaust temperature, and monitored the concentration of PM, NOx, and SO2 in the main atmospheric pollutants in the flue gas. After calculation, the air leakage coefficient when the inspection doors are opened for observation is 0.04. This value still includes the sum of air leakage from coal hopper, furnace door, grate side seal, peep holes and other parts. The monitored average emission concentration of PM decreased by 16.28%, from which we can concluded that the use of thermal imaging technology to monitor the combustion in the furnace is conducive to emission reduction. The application of thermal imaging technology implementation of coal-fired boiler combustion visualization is feasible.

Effect of low nitrogen transformation on energy efficiency of gas fired industrial boilers based on FGR technology

In order to improve air quality and reduce haze, Chongqing has raised the nitrogen oxide emission requirements of gas industrial boilers, reduced the emission limits, and promoted a large number of low-nitrogen transformations of industrial boilers in Chongqing. In this paper, the main generation mechanism of nitrogen oxides and different technical schemes of low nitrogen transformation were introduced. Six representative industrial boilers were selected to carry out low nitrogen transformation based on FGR technology, and nitrogen oxide emission under the reference oxygen content, smoke exhaust temperature, thermal efficiency and actual output of boilers before and after the transformation were compared and tested. The test results show that the actual output of industrial boilers can be reduced and the energy consumption of boilers can be increased by using FGR low nitrogen technology.

Generation of Current in Thermoelectric Generator by Absorption of Heat Using ANSYS Thermal

Thermoelectric power generation is a renewable energy conversion process that directly converts heat to electricity. This research proposes a novel fluid-thermal-electric multi-physics numerical model for predicting the performance of a thermoelectric-producing system. On the ANSYS platform, numerical simulations are done along with the exhaust temperature and mass flow rate. The range of hot end temperatures is from 100 to 450 degrees Celsius. Similarly, the cold end temperature can reach a maximum of 25 degrees Celsius and a minimum of 10 degrees Celsius. When the temperature at the generator's hot end rises, it means the temperature at the generator's cold end must fall. It means both have an inverse relation to each other. The maximum heat absorbed at the hot junction is 32.762 W and the minimum heat absorbed at the hot junction is 4.6305 W. Hence the maximum and minimum current values produced in this paper by the thermoelectric generator are 72.156 A & 10.816 A respectively. The hot side heat exchanger's position of the thermoelectric modules has a significant impact on output. Combining the benefits of many models are advised to construct an inclusive thermoelectric generator system for use in real-world applications.

Thermal Management of Diesel Engine Aftertreatment System Based on Ultra-Low Nitrogen Oxides Emission

To achieve diesel engine ultra-low nitrogen oxide emission, light-off selective catalyst reduction (LO-SCR) has been suggested for better performance with lower exhaust temperature. An electric heater upstream of the exhaust aftertreatment system was applied to significantly decrease the NOx emission at a low exhaust temperature. With a 7.2 kW electric heater coupled with LO-SCR, the NOx emission during 200~500 s of the world harmonized transient cycle (WHTC) decreased from 282.6 ppm to 61.5 ppm, which is a decrease of 45%. Application of an upstream diesel oxidation catalyst (DOC) decreased the NOx emission by 63% at the same interval at the cost of worse cold-start performance. The urea input was also adjusted to avoid NOx emission during the latter part of the WHTC.

Improving the reliability of the turbocharger seal assembly by optimizing the elements of the seal assembly

Currently, most power units using internal combustion engines are equipped with turbocharging and that is explained by the requirements for efficiency, environmental safety and specific power characteristics. At the same time, the turbocompressor (TCR) is one of the resource-determining elements of power units, which accounts for a significant number of failures. Studies conducted towards the analysis of turbocompressor failures have shown that the main reason for it lies in a malfunction of the seal assembly, which is a consequence of extremely unfavorable conditions for its operation, consisting in a high (up to 800 оС) exhaust temperature, aggressive environment, a high (up to 120.000 min-1) rotor speed, the sliding speeds of the mating parts, up to 150 m/s. Oil for lubrication and cooling of the TCR is supplied through floating plain bearings, while the cavities of the turbine and compressor are isolated by means of the seal assemblies. Violation of their operability leads to the ingress of oil in a cavity of the impellers, to the imbalance of a rotor and, ultimately, to a turbocompressor failure. The determining factor affecting the operability of the seal assembly is a heat density of its parts. This factor is especially manifested in operating under forced conditions and engine shutdown, when cooling of a turbine volute is stopped by blown air, and a bearing assembly is stopped by circulating oil. In this case, a large part of the thermal energy is transferred from a heated turbine volute to the seal assembly and to the bearing assembly. The focus is on the temperature influence on performance of the turbocompressors’ sealing rings.

An investigation concerning optimal design of confluent jets ventilation with variable air volume

This parametric study aims to predict the performance of confluent jets ventilation (CJV) with variable air volume (VAV) from four CJV design parameters. A combination of computational fluid dynamics (CFD), and response surface method (RSM) has been used to predict the energy efficiency, thermal comfort and IAQ for the four expected vital design variables, i.e., heat load (XH), number of nozzles (XN), airflow rate (XQ) and supply temperature (XTS). The RSM was used to generate a quadratic equation for the response variables exhaust temperature (TE), supply temperature (TP), PMV, DR, εT and ACE. The RSM shows that the TE, TP and PMV were independent of the number of nozzles. The proposed equations were used to generate setpoints optimized for thermal comfort (PMV) for summer, spring and winter cases with different CLO factors and different TS under a scenario where the heat load varied between 10-30 W/m2. TE was used as setpoint to regulate the airflow rate to keep the PMV values close to zero. The results show that by adapting the TS to the CLO factor both thermal comfort and the energy efficiency can be improved. Further energy reduction can be gained by downregulating the airflow rate to keep the TP at a fixed setpoint when the heat load is decreased. This means that a CJV can effectively be combined with VAV to improve environmental performance with good thermal comfort (-0.5 < PMV < 0.5, DR < 20%), above average IAQ (ACE ≈ 106%) and with a higher heat removal efficiency (ε T ≈110%) than conventional mixing ventilation.

Transient Performance Simulation of Gas Turbine Engine Based on Through-Flow Method and Experimental Verification

Abstract Current research on engine transient performance primarily focuses on the variation of key aerothermodynamic parameters in specific sections, neglecting the comprehensive understanding of the engine's inner flow field during transient operations. To address this gap, this paper proposes a two-dimensional transient simulation method that effectively captures the evolution of the flow field in the meridional plane. The approach involves deriving circumferential averaging equations in a rotating coordinate system with variable angular velocity, considering angular acceleration source terms. The engine components, including the compressor, combustion chamber, turbine, and rotating shaft, are individually modeled. The newly derived governing equations are solved using a dual-time-step approach, where an inner-iteration ensures mass flow conservation, and an outer-iteration updates the rotational speed. Using a real turbojet engine as a case study, transient examinations comprising acceleration and deceleration are performed. A comparative analysis of experimental and simulation results is conducted, revealing an average error of 0.9% in shaft speed, 7.8% in engine thrust, 1.7% in engine exhaust temperature, and 5.1% in compressor outlet pressure. Additionally, the study analyzes and compares the internal flow fields during the transient process, contributing to a deeper understanding of the engine's dynamic behavior. The research effort establishes a practical methodology and technology for conducting comprehensive two-dimensional engine transient cycle analyses within reasonable computational resources and timeframes.

Power prediction and packed bed heat storage control for marine diesel engine waste heat recovery

The generation capability of the waste heat recovery system cannot be fully utilized by relying solely on the exhaust gas, as the mass flow rate and temperature of exhaust fluctuate in real time. The volatility of ship engine conditions and the instability of power demand can pose a challenge to real-time power allocation. Developing integrated prediction and control methods for power allocation becomes necessary. An integrated system is devised to fully utilize waste energy from marine diesel engines by combining a regenerative organic Rankine cycle with a controllable packed bed. The trends of thermodynamic properties and dynamic charging and discharging processes of the system are analyzed. To provide a plausible management strategy for allocating power in real time, a bidirectional long-short-term memory network power prediction method based on improved complete ensemble empirical mode decomposition with adaptive noise and improved marine predator algorithm is proposed. It is found that 315.6 kW of power can be obtained from the system, and its payback period is 6.84 years. In addition, by using the proposed model, the system can reduce diesel engine power generation. The findings suggest the proposed solution is a viable and meaningful strategy.

CITRONELLA OIL AS BIOADDITIVES ON SI ENGINE PERFORMANCE CHARACTERISTICS

Current dynamics of world energy supply have driven various innovations by the industry as well as research communities. Fossil fuels, although experiencing a declining interest due to sustainability issues, remain undeniably crucial since they are nearly irreplaceable in some sectors including electricity generation, it is necessary to continuously establish efforts to improve efficiency of those kinds of fuel. In this work, the authors evaluate the potential of locally sourced essential oils, namely citronella, as a fuel additive in a vision of raising the fuel economy of gasoline RON 90. Citronella oil was selected based on a positive hypothesis deduced from its chemical properties, as mentioned in multiple published works. Tests were made on a generator-set powered by gasoline engine using the mixture of RON 90 and citronella oil of various concentrations as the fuels. In addition, a commercial synthetic additive was also tested alongside the essential oil to provide a comparative figure. Meanwhile other investigators suggest a favorable effect of essential oils, our results show that citronella oil additions lead to higher fuel consumption at the same power level. A similar negative effect was also demonstrated by the synthetic additive. The only sector showing positive results is in terms of exhaust temperature where experiments with citronella additives create lower exhaust temperature as compared to pure gasoline and synthetic additives. However, rooms for innovation remain open by exploring other variables such as higher additive concentrations or combining different kinds of essential oils.

Assessment of exhaust raw emissions and aftertreatment performance in a retrofitted heavy duty-spark ignition engine operating with liquefied petroleum gas

This study investigates the effects of varying Liquefied Petroleum Gas compositions on pollutant emissions and three-way catalyst performance in retrofitted heavy-duty spark-ignition engines. It focuses on fuels with varying propane and butane ratios, providing new insights into the influence of the composition of Liquefied Petroleum Gas on catalyst activity and tailpipe emissions. Representative conditions from the world Harmonized Transient Cycle were selected to comprehensively assess engine emissions and catalyst performance. Experiments under constant and variable λ conditions tested the catalyst's response concerning raw emissions, exhaust temperature, and space velocity, all variables affected by engine operation. Key findings indicate that catalyst performance is not significantly affected by Liquefied Petroleum Gas composition. Under constant λ conditions, the catalyst achieved high conversion efficiency of carbon monoxide, unburned hydrocarbons, and nitrogen oxides, especially under rich conditions (λ = 0.990). However, rich conditions can lead to elevated ammonia levels, although nitrous oxide generation remains low in all circumstances. Implementing λ pulse strategies reduced ammonia formation to around 25 mg/kWh, ensuring high catalyst conversion efficiency for all pollutant species after optimizing the amplitude and frequency of the pulses to establish the balance of reducing-oxidizing species and oxygen storage for each operation mode. Crucially, Liquefied Petroleum Gas composition was determined to be non-critical for the catalyst in these engines, promoting the use of this fuel in retrofitted engines and promoting for a shift towards cleaner transportation.

Experimental study on refrigeration system performance of pure electric refrigerator car based on medium pressure air supply

In view of the low refrigeration efficiency of the refrigeration system of the pure electric logistics car under the high temperature environment, an experimental platform of the refrigeration system based on medium pressure air supply of the pure electric refrigerator car was built with R404A as the refrigerant, the experiment results show that the system refrigerating capacity, COP and EER decrease with the increase of external environment temperature under the same internal environment temperature, the compressor power and exhaust temperature increase with the increase of the external environment temperature. When the external environment temperature is 43 °C, the medium pressure air supply technology is obviously better than the non-air supply technology, the refrigerating capacity increased by 4.1–12.73 %, the compressor power and EER changed little, the COP increased by 1.3–6.38 %, and the exhaust temperature reduced by 3.4 °C-7.11 °C, especially at -3 °C, the system refrigerating capacity decreases by 30.1 %, the compressor power increases by 35.6 %, the COP and EER distribution decreases by 51.24 % and 42.68 %.

A matching method for Twin-VGT systems under varying expansion ratios at high altitudes

In this study, we established a matching method for a twin variable geometry turbocharging (Twin-VGT) system under varying expansion ratios at high altitudes. In addition, we developed an equivalent thermodynamic model of a two-stage variable turbine with the effective flow areas of turbines obtained under velocity constraints for altitudes ranging from 0 to 5500 m. The effects of altitudes on the matching efficacy of a two-stage compressor under different operating conditions were evaluated. Additionally, an optimal distribution of the total boost pressure was determined to minimize the output power of the two-stage compressor during non-isothermal compression at various altitudes. Furthermore, the interplay between exhaust available energy (EAE), total expansion ratio (TER), exhaust temperature, and turbine power was investigated. Lastly, the peak efficiency of the turbocharging system was evaluated by analyzing the distribution of the TER and total enthalpy drop, aimed at optimizing EAE at different altitudes.