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New technologies

Application of OpenFOAM in Product Development Phase

Takeharu Kawamura* Hiroyuki Shiozawa* Masayuki Kogure* Masaharu Onda*

Norihide Miyashita* Misae Hagiwara** Naoki Kitsunezuka**

Takumi Sakamoto** Eikyuu Kin** Sonoko Urushido**

AbstractCalsonic Kansei has Computer-Aided Engineering (CAE) tools extensively due to an ever increasing demand for generating performance prediction in a relatively quick time. It may lead to, however, lengthy analysis modeling and post processing period. In this perspective we have developed OpenFOAM Based Automation System for HVAC (Heating, Ventilation and Air Conditioning) air mix analysis and applied this system to the digital development.

Key Words : CAE, CFD, Simulation / OpenFOAM

1. Introduction Information Technology (IT) have been playing a core role in recent automotive developments, such as those for autonomous and connected cars, and the development style is now changing from conventional Monozukuri ap-proaching model(1). While the finished car manufactures are starting to explore the IT field, the parts suppliers are expected to enhance the ability to support the new Monozukuri technologies. To meet this expectation, we aim to improve the quality of our Monozukuri processes by advancing the product performances, reducing the development cost, and short-ening the lead time. CAE application is the key to such improvements. However, rapidly expanding demands also increase the need for accurate analysis results in large calculation volumes. To fulfill this need with any commercial analysis software, it would continuously incur large expenses to upgrade the software licenses, leading to higher development cost. To tackle this issue, a solution is required to reduce the cost while applying CAE extensively.

2. Requirement of Large Scale/Volume Calculation with OpenFOAM

The previous issue of the Technical Review(2) reported that we verified correlation between commercial fluid analysis software and the open source software called “OpenFOAM.” The verification result concluded that the OpenFOAM is capable of analyzing the HVAC air mix

analysis (Fig. 1 as an example) with equivalent accuracy to the commercial software. This result revealed practi-cality of massive calculation including large scale data processing and optimization with low cost. The next key solution for the software application is to streamline the massive calculation by optimizing the modeling and post-processing operations in order to shorten the anal-ysis period. Thus, we developed an OpenFOAM based automation system for the HVAC air mix analysis that requires massive calculation. Based on the automation system, we have started to use the digital development for reduction of analysis costs.

Static pressureTemperature

Fig. 1 HVAC air mix analysis with OpenFOAM

3. HVAC Temperature Control As shown in Fig. 2, the HVAC consists of an intake blower unit (a) and an Air Conditioner (A/C) unit (b). The HVAC product plays a role of maintaining the occu-

* Global Technology Division, CAE MBE Group** CKE, CAE Analysis Team

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Application of OpenFOAM in Product Development Phase

pant comfort with temperature control functions (heater, cooler, and dehumidifier) and air distribution functions to the cabin. In general A/C units shown in Fig. 3, heat exchangers such as an evaporator (a) and a heater core (b) are installed with an air mix door (c) and air distri-bution doors (d).

(a)Intake blower (b)A/C

Fig. 2 HVAC unit

Fig. 3 Structure of A/C unit

(b)Air distribution control(a)Temperature

Fig. 4 Door functions

Air temperature is controlled based on the opening an-gle of the air mix door (a) shown in Fig. 4, whereas the temperature-controlled airflow is distributed to occupant faces, foot, and/or the front wind shield according to set modes (b). The modes are set to adjust the opening angles of the air distribution doors and to supply the airflow to the designated wind outlet. For the A/C unit designs, performances must be studied for those interactive door functions. In detail, the performance must be verified under the conditions that the opening angles of the air mix door and the air distribution doors are adjusted in combination. To study these performances with CAE software, many analysis patterns must be prepared since the analyses are required for the number of opening angles in combi-nation of the air mix door and the air distribution doors. Furthermore, the number of the operable door angles increases if an independent temperature control function is provided for left and right zones at the front seats or for the rear seats. Preparation of many analysis patterns takes long period and may affect the development lead time. Taking this issue into account, streamlining studies are conducted to automate the lengthy processes.

4. Process Automation Fig. 5 (a) summarizes the operation flow and periods of the conventional HVAC air mix analysis. As illustrated, the pre-process and the post-process take long periods. Thus, we studied for automating these processes to shorten the analysis period. Fig. 6 shows details of the conventional analysis pro-cess. Firstly, the pre-process (Fig. 6 (a)) was studied to shorten the period. The conventional pre-process began with CAD operations where the base shape was mod-ified to arrange the door angles according to design specifications. The modified CAD data was exported in STL format and copied to the calculator machine. Then, calculation conditions were specified for each door angle. In the pre-process, the door angle arrangements in CAD data took significantly longer as the number of door an-gle patterns increased. For streamlining, we put effort on development of a special GUI that allows collectively setting of analysis conditions including the door angles (Fig.7 (a)). As a re-sult, once each door angle is specified in this GUI, it auto-matically converts the angle into geometric coordinates and rotates the door in the CAD shape. Application of this GUI reduces 75% of the pre-process period.

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In line with the pre-process automation, the stream-lining study proceeded to the post-process (Fig.6 (b)). Conventionally, airflow velocity and temperature distri-butions were mapped with manual operation of analysis result viewer software. To draw a graph of outlet air temperature for each door angle, even larger man-hours were required because numerical data were also manu-ally extracted from calculation output with a text editor. To reduce the man-hours, we focused on establishing an automation system so that source data for maps/graphs are automatically extracted when the calculation com-pletes. As a result, once the calculation output is entered in the aforesaid GUI, the analysis result viewer software automatically extracts the map/graph source data. This automation system reduces 83% of the post-process pe-riod. Application of the automation system reduces a half of the entire analysis period (Fig.5 (b)). In the meantime, it is also validated that calculation accuracy of the outlet air temperature is within the range of ±6℃ as report-ed in the previous issue. These facts conclude that the CAE can apply in practical HVAC product development processes. The CAE application leads to deeper perfor-mance studies and brings profound design feedbacks.

Fig. 6 Conventional analysis process

Fig. 7 Automated analysis process

Fig. 5 The effect of the automation

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Application of OpenFOAM in Product Development Phase

5. Concluding Remarks This paper introduced the development of the Open-FOAM based automation system for HVAC air mix anal-ysis. The developed system allows to reduce a half of the analysis period and apply the OpenFOAM in practical product development processes. We will put continuous effort into further improvement of the analysis accuracy with the OpenFOAM and extensive application of the automation technology to other products. Lastly, the author would like to express deep apprecia-tion to all the contributing parties for great cooperation in this study.

References(1) Ministry of Internal Affairs and Communications:

Special Theme: “The Global Paradigm Shift Caused by ICT”, FY 2014 Information and Communications White Paper

(2) Takeharu Kawamura and other authors: Application of OpenFOAM in Product Development Phase (1st Re-port), Calsonic Kansei Technical Review Vol.12 (2016)

TakeharuKawamura HiroyukiShiozawa MasayukiKogure

MasaharuOnda NorihideMiyashita MisaeHagiwara

NaokiKitsunezuka TakumiSakamoto EikyuuKin

SonokoUrushido