Chamber Surface Temperature Research Articles

Piston Crown Profile Modifications for Various Combustion Mode Strategies of Modified GDI Engine towards NOx and PM Reduction

In the current development of automotive engines, the major target is to design a combustion chamber in such a way that the combustion process must provide very less concentrations of emissions. To satisfy current worldwide emission norms, petrol engines also equipped with direct fuel in-jection (gasoline/petrol directly injected into engine cylinder) same as like diesel engines. The main drawback of GDI engine is NOx and PM emissions due to lean burn combustion and rich mixture formation over the combustion chamber surface because of wall wetting. In GDI engines, the gasoline fuel injector is placed at various positions with different angles over an engine cylinder head as per the mode of combustion strategy. Based on the mode of combustion with fuel injection angle, the piston crown shape design in much important that the crown surface must not involved in wall wetting during injection. The piston crown shapes were modified for Spray guided combustion mode, Wall guided combustion mode and Air guided combustion mode by keeping in mind that the position of injector with fuel spray angle and the position of spark plug tip on the cylinder head. The main aim of modifying the crown surface profiles of piston is to impart swirl and squish effects for better mixing of air and injected fuel, maintain combustion chamber surface temperature range within the limits and also to avoid wall wetting results in chances of reducing soot particle/PM emission and NOx emission from combustion process.

Porous frozen material approach to freeze-drying of instant coffee

Porous frozen material with a certain initial porosity was prepared to explore its influence on freeze-drying experimentally. Soluble coffee was selected as the solute in aqueous solution and liquid nitrogen ice-cream making method was used to prepare the frozen materials. Results showed that freeze-drying can be significantly enhanced using the initially porous frozen material compared with the traditionally solid one. By keeping the same sample mass and moisture content with sole radiation heating, drying time of the porous frozen sample was about one third shorter than that of the solid one under the same tested operating conditions. SEM images of dried products revealed that the porous material had a loose and tenuous structure that was favorable to the transportation of sublimated vapor and the desorption of bound moisture. Appropriately increasing the chamber surface temperature benefited the freeze-drying process and changing the chamber pressure had little effect on the process. Combined radiation and conduction heating can further promote the freeze-drying process and save as much as 36.4% of the drying time. The porous frozen material was found to have a wider range of operating temperature and result in relatively lower residual moisture content.

Functional Performance Evaluation of a Novel Thermal Environment Sensor Array

Abstract. The thermal environment (TE) inside livestock and poultry facilities has a substantial impact on animal growth performance and facility energy usage; therefore, the TE must be quantified correctly to maintain the optimal TE that maximizes feed efficiency and consumes minimal resources. To achieve this goal, a TE sensor array (TESA) and accompanying data acquisition system were previously developed to measure dry-bulb temperature (tdb), black globe temperature, airspeed, and relative humidity (RH). While measurement of each parameter is useful individually, it is more informative when they are combined to estimate and assess the total impact that the TE has on an animal. Hence, the objectives of this study were to (1) design, construct, and commission a TE simulation system, named the Animal Thermal Environment Replication and Measurement System (AThERMS), and (2) compare total sensible heat loss estimated by TESA to a reference ideal temperature source (ITS) when subjected to different TE conditions inside AThERMS. AThERMS is a 1.04 × 1.17 × 1.04 m chamber inside a large insulated enclosure in which air supplied by an air handling unit provides unique combinations of tdb, RH, and airspeed while independently controlling chamber surface temperature (ts). Commissioning of AThERMS included qualitative (smoke visualization) and quantitative (three-dimensional traverse) velocity characterizations in the central region of the chamber and verification of similar and stable ts for all six surfaces. Analysis of velocity contours at three nominal flow rates indicated steady patterns, and at three nominal ts values (13°C, 23°C, and 33°C) during 2 h steady-state operation, the maximum average difference between any two of the six surface ts values was 0.26°C. The TESA was then suspended in AThERMS adjacent to the ITS (15.24 cm diameter black copper sphere with a heater immersed in water). The ITS and TESA were subjected to two nominal airspeeds (~0.5 and 2.0 m s-1) at three nominal tdb values (17°C, 25°C, and 33°C) with a mean radiant temperature approximately equal to the nominal tdb. Total heat loss was estimated from heat transfer theory with TESA measurements as inputs and compared to the measured root mean square power required to maintain a constant water temperature in the ITS. Overall, predicted total heat loss underestimated measured power for all six tests. Future work needs to improve the measurement accuracy at low total heat losses. AThERMS can be used to simulate different TEs that an animal may experience and provide steady reference conditions to verify TE measurements. The TESA is a novel and effective tool for understanding the TE distribution and estimating total heat loss. Keywords: Black globe, Data acquisition, Swine, Ventilation.

Impact of a Yttria-Stabilized Zirconia Thermal Barrier Coating on HCCI Engine Combustion, Emissions, and Efficiency

In-cylinder surface temperature has significant impacts on the thermo-kinetics governing the homogeneous charge compression ignition (HCCI) process. Thermal barrier coatings (TBCs) enable selective manipulation of combustion chamber surface temperature profiles throughout a fired cycle. In this way, TBCs enable a dynamic surface temperature swing, which prevents charge heating during intake while minimizing heat rejection during combustion. This preserves volumetric efficiency while fostering more complete combustion and reducing emissions. This study investigates the effect of a yttria-stabilized zirconia (YSZ) coating on low temperature combustion (LTC), efficiency, and emissions. This is an initial step in a systematic effort to engineer coatings best suited for LTC concepts. A YSZ coating was applied to the top of the aluminum piston using a powder air plasma spray (APS) process; final thickness of the YSZ was approximately 150 μm. The coated piston was subsequently evaluated in the single-cylinder HCCI engine with exhaust re-induction. Engine tests indicated significant advancement of the autoignition point and reduced combustion durations with the YSZ coating. Hydrocarbon and carbon monoxide emissions were reduced, thereby increasing combustion efficiency. The combination of higher combustion efficiency and decreased heat loss during combustion produced tangible improvements in thermal efficiency. When the effects of combustion advance were removed, the overall improvements in emissions and efficiency were lower, but still significant. Overall, the results encourage continued efforts to devise novel coatings for LTC.

Numerical Simulation of the Application of Solar Radiant Systems, Internal Airflow and Occupants’ Presence in the Improvement of Comfort in Winter Conditions

In this work, the use of numerical simulation in the application of solar radiant systems, internal airflow and occupants’ presence in the improvement of comfort in winter conditions is made. The thermal comfort, the local thermal discomfort and the air quality in an occupied chamber space are evaluated. In the experimental measurements, a wood chamber, a desk, two seats, two seated hygro-thermal manikins, a warm radiant floor, a solar radiation simulator and a water solar collector are used. The air velocity and the air temperature fluctuation are experimentally evaluated around 15 human body sections. The chamber surface temperature is experimentally measured. In the numerical simulation, a coupling human thermal comfort (HTC) integral model, a computational fluids dynamics (CFD) differential model and a building thermal response (BTR) integral model are applied. The human thermal comfort level is evaluated by the HTC numerical model. The airflow inside the virtual chamber, using the k-epsilon and RNG turbulence models, is evaluated by the CFD numerical model. The chamber surface and the collector temperatures are evaluated by the BTR numerical model. In the human thermal comfort level, in non-uniform environments, the predicted mean vote (PMV) and the predicted percentage of dissatisfied (PPD) people are numerically evaluated; in the local thermal discomfort level the draught risk (DR) is experimentally and numerically analyzed; and in the air quality, the carbon dioxide CO2 concentration is numerically calculated. In the validation tests, the experimental and numerical values of the chamber surface temperature, the air temperature, the air velocity, the air turbulence intensity and the DR are presented.

Effect of micro cooling channels on a hydrogen peroxide monopropellant microthruster performance

In this paper, a hydrogen peroxide monopropellant microthrusters with and without regenerative micro cooling channels were fabricated and performance test results were compared to determine cooling effect of the regenerative micro cooling channels. Photosensitive glass was used as microfabrication material, which is cost-effective for MEMS fabrication process. Nine photosensitive glasses was integrated using UV and thermal bonding and composed the microthrusters. 90wt% hydrogen peroxide was used both as monopropellant and cooling fluid. For hydrogen peroxide decomposition, catalyst was fabricated and inserted into the microchamber. Platinum was used as the catalyst active material and γ-alumina was used as catalyst support. Experimental testing was conducted to determine effect of the cooling channels and the chamber pressure, temperature and surface temperature were measured. The performance test results showed that it was possible to relieve the thermal shock of the micro thruster structure by as much as 64% by adding regenerative micro cooling channels on both sides of the microthruster chamber. However, the chamber pressure and temperature decreased by regenerative cooling channels due to excessive cooling effects.

Experimental investigation of combustion and heat transfer in a direct-injection spark ignition engine via instantaneous combustion chamber surface temperature measurements

An experimental study was performed to provide the combustion and in-cylinder heat transfer characteristics resulting from different injection strategies in a direct-injection spark ignition (DISI) engine. Fast-response thermocouples were embedded in the piston top and cylinder head surface to measure the instantaneous combustion chamber surface temperature and heat flux, thus providing critical information about the combustion characteristics and a thorough understanding of the heat transfer process. Two distinctive operating modes, homogeneous and stratified, were considered and their effect on combustion and heat transfer in a DISI engine was investigated. The stratified operating mode yielded significantly higher spatial variations of heat flux than the homogeneous mode. This behaviour is directly caused by the main features of stratified combustion, i.e. vigorous burning of a close-to-stoichiometric mixture near the spark, and a cool, extremely lean mixture at the periphery. The cooling effect of the spray impinging on the piston surface when the fuel is injected late in compression could be detected too. The local phenomena change with varying speed and injection parameters. Comparison between the calculated global heat fluxes and measured local heat fluxes were performed in order to assess the behaviour of classic heat transfer models. Comparisons between the global and local heat fluxes provide additional insight into spatial variations, as well as indications about the suitability of different classic models for investigations of the heat transfer aspect of DISI engines. Special consideration is required when applying classic heat transfer correlations to stratified DISI operation as heat flux values are lower by more than 30 per cent when compared with homogeneous operation of the same engine at the same load.

Heat transfer in a 155 mm compound gun barrel with full length integral midwall cooling channels

When firing, large amounts of heat flow into the gun bore surfaces and result in wear and erosion of the gun bore. Moreover, the chamber surface temperature will reach the cook-off temperature of propellant during long sustained firing, which will impact on user safety and facilities. For large-caliber gun, a serious limitation on the weapon’s availability for action is imposed with high-energy propellants used and firing rates increasing. An effective method for solving this problem is to adopt barrel liquid-cooling technique. In this paper, heat transfer in a 155 mm midwall cooled compound gun barrel was analyzed theoretically. For the reference, heat transfer in a naturally cooled monobloc gun barrel was also discussed. Finite element analysis (FEA) method was employed to validate the results obtained by theoretical analyses. The present study showed: (1) natural air cooling is ineffective for transferring the heat out of the barrel because the combined convection and radiation heat transfer coefficient is relatively small; (2) forced midwall cooling has great heat extraction capability and is able to keep the chamber temperature below the cook-off temperature by increasing the heat transfer coefficient; (3) an optimal flow rate should be selected to balance the cooling efficiency and the pressure loss.

An Investigation of Thermal Insulation of IDI Diesel Engine Swirl Chambers

The paper describes a computational and experimental study of the application of advanced ceramic materials for thermal insulation of the swirl chamber of the passenger car IDI diesel engine. Four ceramic materials, having a wide range of physical properties, were evaluated. These were syalon 101, aluminium titanate, reaction bonded silicon nitride (RBSN) and tetragonal zirconia polycrystals (TZP). A detailed finite element study was carried out in support of component design which examined parameters such as heat flux, operating temperature, thermal and assembly stresses and evaluated the requirements for interference fits between metallic and ceramic components. Experimental work was initially carried out on a steady state dynamometer test stand and later supported by vehicle tests on a chassis dynamometer and test track. The investigation has shown that current engineering ceramic materials have the potential for application in engine combustion chambers. A total of 254 hours of engine testing with ceramic chambers was achieved without catastrophic engine failure. Engine performance was unchanged by the adoption of a thermally insulated swirl chamber, probably because the increase in swirl chamber surface temperature obtained (increased from 660 to about 850°C at full load) was insufficient to modify the thermodynamic cycle. Hydrocarbon emissions were generally increased, however; this was due in part to the difficulty of sealing the air gap behind the ceramic chamber at the fuel injector and glow plug interfaces.

Combustion of a Diesel Engine with the M-combustion System : Effects of Swirl Ratio and Surface Temperature of Combustion Chamber

This paper gives the experimental results obtained with a two-stroke cycle single-cylinder research engine using an electrically heated combustion chamber to simulate the combustion chamber of a low-heat-rejection(LHR) DI diesel engine with the M-combustion system. In this report, the experiment was performed to investigate the influences of combustion chamber surface temperature and swirl ratio on the combustion of a LHR DI diesel engine with the M-conbustion system. It is found that the combustion of fuel deposited on the surface is greatly affected by the combustion chamber surface temperature, and the diesel combustion is controlled by the swirl and the surface temperature of the combustion chamber.

Combustion of a diesel engine with the M-combustion system. Effects of swirl ratio and surface temperature of combustion chamber.

This paper gives the experimental results obtained with a two-stroke cycle single-cylinder research engine using an electrically heated combustion chamber to simulate the combustion chamber of a low-heat-rejection (LHR) DI diesel engine with an M-combustion system. In this report, the experiment was performed to investigate the influences of combustion chamber surface temperature and swirl ratio on the combustion of an LHR DI diesel engine with an M-combustion system. It is found that the combustion of deposited fuel on the surface is greatly affected by the combustion chamber surface temperature, and the diesel combustion is controlled by the swirl and the surface temperature of the combustion chamber.

Combustion of a diesel engine with the M-combustion system (Effects of injection direction and surface temperature of combustion chamber).

This paper gives the experimental results obtained with a two stroke cycle single cylinder research engine using an electrically heated combustion chamber to simulate the combustion chamber of a low heat rejection DI diesel engine with an M-combustion system. In this report, the experiment was performed to investigate the influences of fuel injection direction, which is cosidered to affect the quantity of deposited fuel on the combustion chamber surface and the influences of combustion chamber surface temperature on the diesel combustion. It is found that the combustion chamber surface temperature greatly affects the combustion of deposited fuel on the surface, and the diesel combustion is controled with the injection direction and the surface temperature of the combustion chamber.

Heat insulated diesel engine with the M-combustion system (Measurements of the combustion chamber surface temperature of heat insulated pistons and its effects on the combustion).

Heat insulated diesel engine with the M-combustion system (Measurements of the combustion chamber surface temperature of heat insulated pistons and its effects on the combustion).

The combustion of a diesel engine with the M-combustion system (Effect of combustion chamber surface temperature)

This paper gives experimental results obtained with a two stroke cycle single cylinder research engine using an electrically heated combustion chamber to simulate the combustion chamber of a low heat rejection DI diesel engine with an M-combustion system. It is concluded that the combustion characteristics of an M-combustion system are greatly affected by surface temperature and the indicated thermal efficiency is significantly improved at higher surface temperatures.

The Performance Potential of Limited Cooled Diesel Engines

A mathematical model is used to predict the performance of a turbocharged diesel engine with a partially insulated combustion chamber. The model is briefly described, with emphasis on heat transfer aspects and prediction of combustion chamber surface temperatures. First the trade-off between performance improvement (efficiency) degree of insulation, combustion chamber surface temperature and exhaust gas energy is examined. It is shown that the high surface temperatures in the cylinder, due to insulation, cause volumetric efficiency to fall. However, this reduction is offset by increased boost pressure from the turbocharger due to greater exhaust gas energy. The contribution to overall reduction in heat loss from cylinder head, piston and liner and their effect on engine efficiency are presented and discussed. Various turbo-compound systems are examined and it is shown that most systems become unmatched when working over the wide speed and load range necessary for vehicle application, unless a variable geometry turbine or a variable ratio gearbox (this maintains compound power at part load) are used. Furthermore, substantial overall performance benefits can only be obtained with very efficient turbomachinery. Rankine bottoming cycles are more effective than fixed geometry turbo-compounding at low load, but their normal efficiency is limited by high condenser temperature, and they would be difficult to install in a compact European truck. It is concluded that the ultimate improvement in engine specific fuel consumption of an adiabatic turbo-compound engine is 20 per cent (excluding the savings from fan and water pump). However, drastically new design concepts are necessary, if engines are to be built that approach this degree of insulation. Meanwhile redesigned conventional engine types will offer substantial reduction in cooling system requirements with more modest thermal efficiency benefits.

Measurements of Convective and Radiative Heat Transfer in Small Mammals

The coefficient of convection and the effective surface area for the emission and absorption of thermal radiation are two physical characteristics of an organism that must be quantified before the energy budget of that organism can be calculated. These two parameters were measured by using internally heated, pelt-covered metal casts of four species of western chipmunks ( Eutamias alpinus, E. speciosus, E. amoenus , and E. minimus ). The casts were suspended in a vacuum and the effective radiating surface area (Aee) was calculated from the wattage necessary to maintain a constant cast radiating surface temperature ( Tr ), Tr , and chamber surface temperature. The casts were placed in a wind tunnel and the coefficients of convection at different wind speeds were calculated from Tr , wattage necessary to maintain that Tr, air temperature, tunnel wall temperature, and total cast surface area.