Turbulent Properties in Ic Engine Derived From Wall Heat Flux Measured With a Three Point Thin Film Sensor

Nakamura

et al. 2018

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A heat flux sensor was developed with micro-electro-mechanical systems (MEMS) technologies for investigating turbulent heat transfer characteristics in engines. The sensor has three thin-film resistance temperature detectors (RTDs) of a square 315 µm on a side on a 900 µm diameter circle in rotational symmetry. The performances of the MEMS systems sensor were tested in an open combustion chamber and a laboratory engine. In the open chamber tests, it was revealed that the MEMS sensor can measure the wall heat fluxes reflecting flow states of gas phase. In addition, the noise was evaluated as 3.8 kW/m2 with the standard deviation against the wall heat flux of a few hundred kW/m2. From these results, it was proved that the MEMS sensor has the potential to observe turbulent heat transfer on the order over 10 kW/m2 in the engine. In the laboratory engine test, the wall heat flux for continuous 200 cycles was measured with a good signal-to-noise ratio. The noise was evaluated as 13.4 kW/m2 with the standard deviation despite the noisy environment. Furthermore, it was proved that the MEMS sensor has the comparable scale with the turbulence in the engine because the three adjacent detectors measured similar but different phase oscillations in the local instantaneous heat fluxes. In addition, a heat flux vector reflecting the state of the local instantaneous heat transfer was visualized by the adjacent three-point measurement. It is expected that the three-point MEMS sensor will be a useful tool for the engine heat transfer research.

Section: Introductionmentioning

confidence: 99%

Three-point MEMS heat flux sensor for turbulent heat transfer measurement in internal combustion engines

Nakamura

et al. 2018

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“…The details of the calculation method are further elaborated in literatures. 13,15 In the following, the estimation of the flow characteristics is briefly described with respect to the data between 30° < CA < 60° shown in Figure 5 as an example. Note that the estimated values are the mean values over the analysis duration, namely, 30° < CA < 60° in this case.…”

Section: Attempt Of Estimating Flow Characteristics From Wall Heat Fluxesmentioning

confidence: 99%

“…Data got from these were used to estimate the gas phase information in the vicinity of a wall. 13,15 In this article, the flow characteristics estimated from wall heat fluxes measured in a laboratory engine are reported. Suppose that the information about the flow as well as the heat transfer is extracted through the wall side measurements, then the relationship between them will be investigated more easily.…”

Section: Introductionmentioning

confidence: 99%

“…Data got from these were used to estimate the gas phase information in the vicinity of a wall. 13,15…”

Section: Introductionmentioning

confidence: 99%

“…In this study, the advective velocity of the turbulent eddies in the wall parallel direction u and the turbulent eddy scale d were estimated from the heat flux fluctuations. The details of the calculation method are further elaborated in literatures 13,15. In the following, the estimation of the flow characteristics is briefly described with respect to the data between 30°\ CA \ 60°shown in Figure5as an example.…”

mentioning

confidence: 99%

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Attempt of estimating flow characteristics from wall heat fluxes measured using a three-point micro-electro-mechanical systems sensor

2020

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In this study, it was attempted to estimate the flow characteristics in the vicinity of an engine inner wall from the instantaneous local heat fluxes measured using a micro-electro-mechanical systems sensor. As the sensor has three resistance temperature detectors with a size of 315 µm fabricated on a circumference with a diameter of 900 µm in rotational symmetry, it can measure local heat flux on the equivalent scale of the turbulence of in-cylinder flow. The advective velocity and turbulent eddy scale were estimated from heat flux fluctuations using a cross-correlation analysis, and these were compared with results of particle image velocimetry performed under motored operation conditions. As a result, it was found that the micro-electro-mechanical systems sensor has the potential to detect the gas side information such as the wall parallel flow velocity. Although further verification of the physical meanings of the estimated characteristics is necessary, the micro-electro-mechanical systems sensor will become a powerful tool for engine diagnostics.

Application of a MEMS heat flux sensor to heat transfer research on an impinging diesel jet

Moussou

et al. 2021

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To clarify the mechanisms of heat transfer on an engine wall is an important challenge because the heat loss on the wall is one of the dominant factors that limit the thermal efficiency. A thin-film resistance type heat flux sensor fabricated with Micro-Electro-Mechanical Systems (MEMS) technologies was applied to research on the heat transfer of an impinging diesel jet. The MEMS sensor had a high sensitivity and multiple measurement points with a scale comparable to the turbulence of in-cylinder flow for the investigation of local instantaneous heat transfer characteristics in engines. Measurements of wall temperature and heat flux were conducted in a constant volume chamber under the reference conditions of Engine Combustion Network (ENC) Spray A with variations in injection pressure. As a result, the maximum heat flux and heat transfer coefficient reached about 5 MW/m2 and 3 MW/(m2 K), respectively. The results were compared to those obtained with a commercially available thermocouple, and both sensors produced similar trends. In addition, fluid motion near the wall was estimated from the heat flux fluctuations using a cross-correlation analysis. The relationship between heat transfer and flow was investigated in a dimensionless number fashion, and it was compared to a semi-theoretical prediction that was based on a steady state laminar flow heat transfer model.