Low Heat Rejection Engine Research Articles

A comparative evaluation of Al2O3 coated low heat rejection diesel engine performance and emission characteristics using fuel as rice bran and pongamia methyl ester

In this study, for the first time, a nanoceramic Al2O3 was used as a coating material in the low heat rejection engine concept. Experiments were conducted on single cylinder, four stroke, water cooled, and direct injection diesel engine. First, the engine was tested at different load conditions without coating. Then, combustion chamber surfaces (cylinder head, cylinder liner, valves, and piston crown face) were coated with nanoceramic material of Al2O3 using plasma spray method. Comparative evaluation on performance and emission characteristics using fuel as rice bran methyl ester, pongamia methyl ester, and biodiesel/diesel fuel mixtures was studied in the ceramic coated and uncoated engines under the same running conditions. An increase in engine power and a decrease in specific fuel consumption, as well as significant improvements in exhaust gas emissions (except NOx) and smoke density, were observed in the ceramic coated engines compared with those of the uncoated engine.

Performance characteristics of a glowplug assisted low heat rejection diesel engine using ethanol

Conventional diesel engines with ethanol as fuel are associated with problems due to high self-ignition temperature of the fuel. The hot surface ignition method, wherein a part of the injected fuel is made to touch an electrically heated hot surface (glowplug) for ignition, is an effective way of utilizing ethanol in conventional diesel engines. The purpose of the present study is to investigate the effect of thermal insulation on ethanol fueled compression ignition engine. One of the important ethanol properties to be considered in the high compression ratio engine is the long ignition delay of the fuel, normally characterized by lower cetane number. In the present study, the ignition delay was controlled by partial insulation of the combustion chamber (low heat rejection engine) by plasma spray coating of yttria stabilized zirconia for a thickness of 300 μm. Experiments were carried out on the glowplug assisted engine with and without insulation in order to find out the possible benefits of combustion chamber insulation in ethanol and diesel operation. Highest brake thermal efficiency of 32% was obtained with ethanol fuel by insulating the combustion chamber. Emissions of the unburnt hydrocarbons, oxides of nitrogen and carbon monoxides were higher than that of diesel. But the smoke intensity and was less than that of diesel engine. Volumetric efficiency of the engine was reduced by a maximum of 9% in LHR mode of operation.

The effects of Al 2O 3–TiO 2 coating in a diesel engine on performance and emission of corn oil methyl ester

Today, as a result of increase in oil prices, limited fossil fuel resources, environmental consideration and global warming, the methyl ester fuels have been focused on alternative fuels. Methyl ester fuels can be used more efficiently in low heat rejection engines (LHR), in which the temperature of combustion chamber is increased by creating a thermal barrier. In this study, the piston, cylinder head, exhaust and inlet valves of a diesel engine were coated with the ceramic material Al 2O 3–TiO 2 by the plasma spray method. Thus, a thermal barrier was provided for the parts of the combustion chamber with these coatings. The effects of corn oil methyl ester that produced by the transesterification method, and No. D2 fuels’ performance and exhaust emissions’ rate were studied by using equal in every respect coated and uncoated engines. Tests were performed on the uncoated engine, and then repeated on the coated engine and the results were compared. A decrease in engine power and specific fuel consumption, as well as significant improvements in exhaust gas emissions (except NOx), were observed for all test fuels used in the coated engine compared with that of the uncoated engine.

Performance studies of a low heat rejection engine operated on non-volatile vegetable oils with exhaust gas recirculation

During recent decades, considerable effort has been expended world-wide to reduce dependency on petroleum fuels for power generation and transportation through the search for suitable alternative fuels that are environmentally friendly. In this respect, vegetable oils are a promising alternative to diesel fuel. However, the high viscosity, poor volatility and cold flow characteristics of vegetable oils can cause some problems such as injector coking, severe engine deposits, filter gumming and piston ring sticking and thickening of lubrication from long-term use in diesel engines. These problems can be eliminated or minimised by transesterification of the vegetable oils to form monoesters. Although transesterification improves the fuel properties of vegetable oil, the viscosity and volatility of biodiesel are still worse than those of petroleum diesel fuel. The performance of a diesel engine with such biodiesel operation can be improved further with the concept of the low heat rejection (LHR) engine. In the LHR engine, combustion surfaces on the pistons, cylinder walls and valves can be coated with ceramic materials. The objective of this study was to apply the LHR engine concept for improving engine performance when either honge biodiesel, known as honge oil methyl ester (HOME), or neem biodiesel, known as neem oil methyl ester (NOME) oils was used as an alternative fuel. For this purpose, experiments were conducted on a single cylinder, four-stroke, direct injection, water-cooled compression ignition engine using diesel, HOME and NOME oils at different injection timings of 19, 23 and 27° before top dead centre (BTDC) with and without the induction of exhaust gas recirculation (EGR). The percentage of EGR was varied from 5 to 20% in steps of 5%. The results showed that specific fuel consumption and brake thermal efficiency were improved for both of the biodiesel fuels in the LHR engine. An EGR of 10% resulted in better performance with trade-off between oxides of nitrogen and hydrocarbons/carbon monoxide emissions and hence 10% EGR is taken as the best of the range from 5 to 20%. However, readings with other EGR ratios are not reported.

Performance of a low heat rejection engine fuelled with low volatile Honge oil and its methyl ester (HOME)

Energy conservation and efficiency have always been the quest of engineers concerned with internal combustion (IC) engines. A diesel engine generally offers better fuel economy than its counter part petrol engines. It rejects about two-third of heat energy of the fuel to the coolant and one-third to the exhaust, leaving only about one-third as useful power output. Theoretically if the heat rejected could be reduced, then thermal efficiency would improve, at least up to the limits set by the second law of thermodynamics. The main objective of low heat rejection (LHR) engines is to improve the thermal efficiency by reducing the heat lost to the coolant. Diesel engines with their combustion chamber walls insulated by ceramics are referred to as LHR engines. To meet increasing energy requirements, there has been growing interest in alternative fuels like biodiesels derived from vegetable oils to provide a suitable diesel oil substitute for IC engines. Vegetable oils present a very promising alternative to diesel oil since they are renewable and have similar properties. Vegetable oils offer almost the same power output with slightly lower thermal efficiency when used in a diesel engine. In view of this, Honge oil, being non-edible, could be regarded as an alternative fuel for compression ignition (CI) engine applications. The viscosity of Honge oil is reduced by transesterification to obtain Honge oil methyl ester (HOME). In the present work, an attempt has been made to utilize the low volatile Honge oil and HOME in a CI engine to study the performance, combustion, and emission characteristics with a ceramic coating of partially stabilized Zirconium (PSZ) on combustion chamber elements. Initial experiments were conducted on a single cylinder, direct injection, four stroke, water-cooled CI engine without LHR using diesel, Honge oil and HOME to determine optimum injection timings and injection pressures. The optimum values of injection timings were found to be 23° before top dead centre (BTDC) for diesel and 19° BTDC for Honge oil and HOME. Optimum injection pressures were 260 and 205 bar for Honge oil and HOME, respectively. The results obtained showed decrease in brake thermal efficiency and increase in emissions for Honge oil operation compared with conventional diesel engine operation. However, with HOME marginal improvement in brake thermal efficiency and reduction in emissions were observed when compared with Honge oil operation. Further tests were conducted on the CI engine for Honge oil and HOME with ceramic coating on combustion chamber surfaces. The results obtained showed improvement in brake thermal efficiency and reduction in emissions. The effect of injection timings/injection pressures on combustion, rate of heat transfer, cumulative heat transfer, combustion duration and delay period have been considered and analysed for the overall performance of LHR and conventional diesel engines for different fuels tested. However, results obtained with optimum injection timing and injection pressure have only been presented.

Optimization of an Irreversible Diesel Cycle: Experimental Results of a Ceramic Coated Indirect-Injection Supercharged Diesel Engine

In this work, an irreversible dual cycle analysis has been performed for enhancing the characteristics of a low heat rejection (LHR) supercharged single-cylinder indirect-injection (IDI) diesel engine. A relation which gives the maximum power (MP) and the corresponding efficiency has been derived analytically. Optimization of the diesel cycle has been performed for power and thermal efficiency with respect to the pressure ratio and temperature ratio. Optimum values of the pressure ratio and cutoff ratio of the diesel cycle, depending on the temperature ratios, have been derived analytically and compared to the results of an experimental study of the LHR engine, whose optimum performance was obtained by increasing the temperature in the combustion chamber. Effects of a ceramic coating on performance and exhaust emissions in the LHR engine have been compared to those obtained from the standard (STD) diesel engine based on the comparison of the STD and the LHR engines for identical airflow and brake mean effective pressure. Intake pressure was adjusted to give the same air consumption as the corresponding STD engine for the same brake mean effective pressure (BMEP) and engine speed to avoid a reduction in the volumetric efficiency of the LHR engine. In comparison to the STD engine, satisfactory performance was obtained with the LHR engine. Specific fuel consumption was decreased up to 4.5%, and brake efficiency was increased by 1.5%. NOx emissions were increased by 12% because of the higher flame temperature in the LHR engine.

First and second law analysis of low heat rejection diesel engine

In this study, a comparative first and second law analysis of a turbocharged diesel engine was performed. The main aim was to investigate the impact of thermal insulation on energy, and exergy balances of the engine. For this reason, both standard (STD) and low heat rejection (LHR) engines were thermodynamically analysed. Over the range of operating conditions investigated, the second law efficiencies of the STD and the LHR engines were found to vary from 30·70 to 44%, and 32 to 45·75% respectively. The second law efficiency of LHR diesel engine was 2·85% higher than that of STD diesel engine. The available exhaust energy of the LHR engine was also up to 12% higher. It is concluded that an additional exhaust recovery system, such as turbocompound and/or Rankine bottoming cycle should be used to improve a LHR engine performance.

Performance characteristics of a low heat rejection diesel engine operating with biodiesel

Vegetable oils are a promising alternative among the different diesel fuel alternatives. However, the high viscosity, poor volatility and cold flow characteristics of vegetable oils can cause some problems such as injector coking, severe engine deposits, filter gumming, piston ring sticking and thickening of lubrication oil from long-term use in diesel engines. These problems can be eliminated or minimized by transesterification of the vegetable oils to form monoesters. These monoesters are known as biodiesel. The important advantages of biodiesel are lower exhaust gas emissions and its biodegradability and renewability compared with petroleum-based diesel fuel. Although the transesterification improves the fuel properties of vegetable oil, the viscosity and volatility of biodiesel are still worse than that of petroleum diesel fuel. The energy of the biodiesel can be released more efficiently with the concept of low heat rejection (LHR) engine. The aim of this study is to apply LHR engine for improving engine performance when biodiesel is used as an alternative fuel. For this purpose, a turbocharged direct injection (DI) diesel engine was converted to a LHR engine and the effects of biodiesel (produced from sunflower oil) usage in the LHR engine on its performance characteristics have been investigated experimentally. The results showed that specific fuel consumption and the brake thermal efficiency were improved and exhaust gas temperature before the turbine inlet was increased for both fuels in the LHR engine.

Experimental study of NO x emissions and injection timing of a low heat rejection diesel engine

In this study, an experimental study of the effects of injection timing on nitrogen oxide (NO x ) emissions of a low heat rejection (LHR) turbocharged direct injection diesel engine was conducted. The injection timing and brake specific fuel consumption (BSFC) trade-off must be considered together in performance and NO x emissions analysis. For the original injection timing of the 20° before top dead centre, the brake specific fuel consumption value of the LHR engine was approximately 6% lower than the original engine. NO x emissions were also higher (about 9%) than the original engine. To reduce NO x emissions released by diesel engines, the method of injection timing retard was utilized. Thus, the LHR engine was tested for two different injection timings; 18° and 16° crank angle before top dead centre (BTDC), at the same engine speeds and load conditions. The results showed that the BSFC and NO x emissions were reduced 2% and 11%, respectively by retarding the injection timing. Optimum injection timing for the LHR engine was obtained through decreasing by 2° BTDC.

Cylinder wall insulation effects on the first- and second-law balances of a turbocharged diesel engine operating under transient load conditions

During the last decades there has been an increasing interest in the low heat rejection (LHR) diesel engine. In an LHR engine, an increased level of temperatures inside the cylinder is achieved, resulting from the insulation applied to the walls. The steady-state, LHR engine operation has been studied so far by applying either first- or second-law balances. Only a few works, however, have treated this subject during the very important transient operation with the results limited to the engine speed response. To this aim an experimentally validated transient diesel engine simulation code has been expanded so as to include the second-law balance. Two common insulators for the engine in hand, i.e. silicon nitride and plasma spray zirconia are studied and their effect is compared to the nominal non-insulated operation from the first- and second-law perspective. It is revealed that after a step increase in load, the second-law values unlike the first-law ones are heavily impacted by the insulation scheme applied. Combustion and total engine irreversibilities decrease significantly (up to 23% for the cases examined) with increasing insulation. Unfortunately, this decrease is not transformed into an increase in the mechanical work but rather increases the potential for extra work recovery owing to the higher availability content of the exhaust gas.

Effects of thermal barrier coating on gas emissions and performance of a LHR engine with different injection timings and valve adjustments

Tests were performed on a six cylinder, direct injection, turbocharged Diesel engine whose pistons were coated with a 350 μm thickness of MgZrO 3 over a 150 μm thickness of NiCrAl bond coat. CaZrO 3 was employed as the coating material for the cylinder head and valves. The working conditions for the standard engine (uncovered) and low heat rejection (LHR) engine were kept exactly the same to ensure a realistic comparison between the two configurations of the engine. Comparisons between the standard engine and its LHR version were made based on engine performance, exhaust gas emissions, injection timing and valve adjustment. The results showed that 1–8% reduction in brake specific fuel consumption could be achieved by the combined effect of the thermal barrier coating (TBC) and injection timing. On the other hand, NO x emissions were obtained below those of the base engine by 11% for 18° BTDC injection timing.

The effects of injection timing on NO x emissions of a low heat rejection indirect diesel injection engine

Higher NO x is one of the major problems to be overcomed in a low heat rejection (LHR) diesel engine as insulation leads to an increase in combustion temperature about 200–250 °C compared to an identical standard (STD) diesel engine. High combustion temperatures alter optimum injection timing of a LHR engine. With the proper adjustment of the injection timing, it is possible to partially offset the adverse effect of insulation on heat release rate and hence to obtain improved performance and lower NO x . However, the injection timing and brake specific fuel consumption (BSFC) trade-off must be considered together in performance and NO x emission point of view. In this study, optimum injection timing was found with 4 crank angle (34° CA) retarded before top dead centre (BTDC) in LHR diesel engine in comparison to that of STD diesel engine (38° CA BTDC). When the LHR engine was operated with the injection timing of the 38 crank angle, which is the optimum value of the STD engine, it was shown that NO x emission increased about 15%. However, when the injection timing was retarded to 34° CA in the LHR case, it was observed a decrease on the NO x emissions with about 40% and the brake specific fuel consumption (BSFC) with about 6% compared to that of the STD case. Thus, by retarding the injection timing, an additional 1.5% saving in fuel consumption was obtained.

시뮬레이션 프로그램에 의한 소형 선박용 저열손실 디젤엔진의 성능평가

It is known that over 60% of engine power is dissipated into circumstance, cooling water and cooling oil without any conversion into useful work. Following the first law of thermodynamics, it is possible that heat loss to cooling water can be converted into mechanical work through crankshaft. But in case that the engine is operating without any cooling effect, the serious problem unsolved so far is the engine durability. In this study, LHR(Low Heat Rejection) engine was introduced as one of the promising engine and several useful qualitative and quantitative data were drawn.

The effect of thermal barrier coating on a turbo-charged Diesel engine performance and exergy potential of the exhaust gas

Abstract In this study, the effect of insulated combustion chamber surfaces on the turbocharged, direct injection Diesel engine performance was experimentally investigated. Satisfactory performance was obtained with the low heat rejection (LHR) engine. In comparison to a standard Diesel engine, specific fuel consumption was decreased by 6%, and brake thermal efficiency was increased by 2%. It was concluded that the exhaust gas process was the most important source of available energy, which must be recovered via secondary heat recovery devices. The available exhaust gas energy of the LHR engine was 3–27% higher for the LHR engine compared to the standard (STD) Diesel engine. However, it is impossible to recover all the exhaust gas energy in useful work. It is found that the maximum extractable power is less than 47% of the exhaust power.

The effect of heat transfer on performance of the Diesel cycle and exergy of the exhaust gas stream in a LHR Diesel engine at the optimum injection timing

In this study, a Diesel cycle analysis taking combustion and heat transfer into account on performance has been performed. The effect of heat transfer is analysed in terms of design parameters such as compression ratio and cut-off ratio. The effects of heat transfer from the cylinder on exhaust temperature were also investigated for different heat transfer and combustion modes. It was observed that the work output and exhaust temperature proportionally increase with the decrease of heat transfer for a fixed combustion rate and cut-off ratio. In the experimental study, it was found that the minimum fuel consumption in the LHR engine compared to the standard (STD) engine was obtained with a 4° crank angle (CA) retardation of the injection timing from the 38° (CA). The decrease in specific fuel consumption at this injection timing reached 6%, and the increase in brake thermal efficiency was 2%. The exhaust temperature of the LHR Diesel engine with the injection timing of 38° CA was 10.8% higher than that of the STD engine, whereas, the increase in the temperature reached 22.8% at 34° CA. Thus, as a consequence of its great potential for optimisation of system performance, a comparative exergy analysis has been performed with the purpose of calculating the amount of available energy of the exhaust gas stream at the optimum injection timing (34 CA) for the LHR engine. While the maximum amount of available energy in the LHR engine exhaust gas stream with the injection timing of 38° CA was 13.45%, the increase at the optimum injection timing of 34° CA was found to reach 38%. It was concluded that the exhaust gas stream of a low heat rejection (LHR) Diesel engine is the most important source of available energy, which must be recovered via a secondary heat recovery system.

Performance and exhaust emission characteristics of a lower compression ratio LHR Diesel engine

In this study, the effects of reducing the compression ratio on the performance and exhaust emissions in a low heat rejection (LHR) indirect injection Diesel engine have been experimentally compared to those obtained from a standard Diesel engine (SDE) with fixed compression ratio. Reducing the compression ratio in a SDE without making any modification in the combustion chamber geometry and improvements in fuel properties cause the ignition delay time to be unduly long, and consequently, an unacceptable pressure rise is experienced. By means of high temperature increases in the combustion chamber of the LHR Diesel engine, the compression ratio was lowered from 18.20 to 16.10 in 0.7 intervals. Satisfactory performance was obtained at compression ratios of 17.50 and 16.80 in the LHR engine. In comparison to the SDE, at these compression ratios, the specific fuel consumption and NO x emissions are, respectively, decreased about 2.9% and 15%.

Performance and emissions characteristics of a partially insulated gasoline engine

This paper presents the work continued from the previous study on a low heat rejection (LHR) engine. Instead of using a single-property yttria-stabilized zirconia (YSZ) coating to achieve the thermal barrier for the piston crown, a varying-properties functionally graded material (FGM) was used in this study. Extensive experiments were conducted on a 3-cylinder SI Daihatsu engine with all piston crowns coated with a layer of ceramic, which consists of zirconia and yttria with varying compositions along its thickness. Measurements of engine performance, in particular its fuel consumption and emissions characteristics, were made before and after the application of FGM coatings onto the piston crowns. To gain more insight of improved engine performance, in-cylinder pressure measurements were conducted which provide direct comparison of pressure–volume diagrams between baseline and that coated with FGM.

The Effect of Thermal Barrier Coated Piston Crown on Engine Characteristics

While there have been numerous research papers in recent years describing the theoretical benefits obtained from the use of ceramic components in reciprocating engines, the amount of literature that describes practical results is very limited. Although successes have been reported and ceramic components are now in service in production engines, mainly for reduced in-cylinder heat rejection, many researchers have experienced failures or a drop in engine performance. This article presents the work completed on a low heat rejection engine. Extensive experiments were conducted on a three-cylinder SI Daihatsu engine with piston crowns coated with a layer of ceramic, which consisted of yttria-stabilized zirconia (YSZ). Measurement and comparison of engine performance, in particular fuel consumption, were made before and after the application of YSZ coatings deposited onto the piston crowns. The details of the cylinder pressures during the combustion process were also investigated.

Instantaneous Heat Flux Flowing into Ceramic Combustion Chamber Wall Surface of Low Heat Rejection Engine.

Instantaneous Heat Flux Flowing into Ceramic Combustion Chamber Wall Surface of Low Heat Rejection Engine.

Development of Thin-Film Thermocouple Measuring for Instantaneous Heat Flux Flowing into the Ceramic Combustion Chamber Wall.

In order to evaluate the validity of a low heat rejection engine proposed for the reduction of heat loss, a thin film thermocouple was developed for accurate measurement of the instantaneous heat flux flowing into the ceramic combustion chamber wall. The thin film thermocouple is the pair-wire type construction without effects of the material of the thermocouple and the instantaneous heat flux, which was confirmed by finite element analysis. This paper also shows examples of measurements conducted on the instantaneous heat flux flowing into the ceramic combustion chamber, using the pairwire type thin film thermocouple made of ceramic base material.