【作者】 王娟；

【导师】 陈海峰；

【作者基本信息】 陕西科技大学 ， 化工过程机械， 2016， 硕士

【摘要】 水果和蔬菜营养价值高,其成分中包含的各种维生素、植物纤维和生物酶等对人体健康十分有利。我国是农产品生产与消费大国,果蔬资源在世界范围内位居首位。近年来果蔬产业发展迅猛,2011年蔬菜总产量已经超过粮食,成为我国第一大农产品,果蔬产业成为我国农业中的支柱型产业。但果蔬品在储藏和运输环节由于方法不当损耗较大,造成果蔬资源大量浪费。因此开展和研发果蔬深加工技术,对提高果蔬资源利用率,增加果蔬产业利润,促进产业良性发展具有重要的意义。低温高压气流膨化干燥技术是近年来新兴的一种果蔬加工技术,由于果蔬膨化产品无油脂无添加剂,口感酥脆,较好地保存了果蔬原有的营养物质,这项深加工技术也越来越受到大家的关注。本文以低温高压膨化干燥技术为研究对象,总结分析了近几十年来国内外关于该技术的研究进展。针对现有的膨化工艺和设备中存在的不足,从改善产品质量,提高生产效率和能量利用率等角度出发,提出改进方案。对生产工艺进行改进,提出了氮气高压渗透膨化工艺方案。即由气爆脱壳技术联想到利用氮气分子在高压的作用下,通过果蔬毛细孔缓缓渗入到组织内部,保持高压一定时间,迅速泄压后由于果蔬内外压差和毛细孔的阻滞作用,使得果蔬发生膨化。为验证新工艺的可行性,采用苹果片为膨化原料,搭建起相应的试验平台,试验结果表明采用氮气渗透膨化技术可以实现苹果片膨化过程。通过单因素试验,初步确立了工艺操作参数。之后进行二次正交旋转组合试验,建立了膨化压差、膨化温度和抽空时间对含水量,复水比,膨化度的二次回归方程模型,分析结果表明该数学模型可靠。通过响应面分析得出了操作参数的交互作用对产品品质的影响规律,最后进行参数优化得到氮气渗透膨化的最佳工艺参数值。对膨化设备进行改进,针对现有间歇式设备存在的生产周期长,生产产量低等问题,提出一种连续式渗透膨化设备方案。简要地阐述了新型连续式膨化设备的工作原理,设计确定连续设备的总产量。结合前期试验确定的操作参数值,对连续式设备进行设计,包括对膨化壳体、旋转料框、端面和径向密封件、真空罐和支座等部件的设计计算,以及对传动机构的选型设计等。采用ANSYS软件对连续式高压膨化设备的膨化壳体、旋转料框及支座进行了有限元分析。根据分析结果,壳体的最大等效应力发生在出料口位置,其值小于材料的许用应力值,最大变形量较小;在对不同厚度挡板的旋转料框逐一进行应力应变分析后得出,当厚度选择20mm和30mm时,最大等效应力值超过材料需用应力值且最大变形量过大,而当厚度为40mm,50mm时,结构强度满足要求,为减轻设备重量考虑,优先选择了40mm厚度的料框结构;对改型设计的支座进行受力分析,支座最大应力值和变形量均较小,结构强度满足要求。更多还原

【Abstract】 Fruits and vegetables are high in nutritious value.Various vitamins, enzymes and plant fiber which are contained in its content are good to the human health.Our country is a large agricultural country in production and consumption, the resource of fruits and vegetables rank first around the world. In recent years, the industries of fruits and vegetables are developing rapidly. Since 2011, the total output of vegetable has exceeded that of grain, vegetable become China’s first major agricultural product, the industry of fruit and vegetable become pillar industry of China’s agriculture. But due to improper method in storage and transportation, the loss of fruits and vegetables is bigger, which causes massive waste of resources. Therefore, the research and development of deep processing technology on fruits and vegetables are of vital significance to improve the utilization rate of fruit and vegetable resources, to increase the profits of industry and to promote the sound development of industry. The technology of air flow puffing drying at low-temperature and high-pressure is a new kind of fruit and vegetable processing technology which is emerging in recent years. For the products after puffing drying have low fat, no additives and crisp taste, at the same time they can well keep the original nutrients in vegetables, the processing technology has drawn greater attention by all of us.Based on puffing drying technology at low-temperature and high-pressure as the research object, this article summarizes the research progress about the technology at home and abroad in recent decades. In view of the shortcomings in existing puffing technology and equipment, the improvement scheme is put forward for improving the quality of the product, increasing production efficiency and energy utilization.To improve the production technology, the scheme of infiltration puffing by high-pressure nitrogen is proposed. The inspiration comes from the shelling technology by gas burst. Under high pressure, nitrogen molecules can slowly seep into the organization through the pores of fruit and vegetable, and keep theenvironment of high pressure for some time, quickly release the pressure, then puffing process has been completed because of the internal-external pressure difference of fruit and vegetable and retardation of pores. To test and verify the feasibility of new technology, corresponding test platform is set up with apple slices as raw materials. The test results show that the technology of infiltration puffing by high-pressure nitrogen can realize puffing process on apple slices.Through single-factor experiment, process operating parameters are preliminary established. After quadratic orthogonal rotation combination experiment, the quadratic regression equation model is established for puffed differential pressure, puffing temperature and vacuum drying time to water content, recovery ratio, swelling degree. The analysis results show that the mathematical model is reliable. The influence rule of the interaction of operating parameters to the product quality is obtained through response surface analysis. Finally, the best values of process parameter for infiltration puffing have been obtained by parameter optimization.To improve puffing equipment, the scheme for a kind of continuous infiltration puffing equipment is proposed in view of existing batch equipment’s problems for long production cycle and low output. This paper briefly expounds the working principle of new type of continuous puffing equipment, the total output of continuous equipment is defined. According to the values of operation parameter determined in the previous test, the continuous equipment has been designed, including the design and calculation of expansion shell, rotating material box, transverse and radial seal and vacuum tank and bearing, and selection of transmission mechanism etc.The finite element analysis of expansion shell, rotating material box and bearing on continuous equipment have been carried on by ANSYS software.According to the results of the analysis, the position for maximum equivalent stress of shell locates at the discharge hole. Its value is less than the allowable stress of material and the value of maximum deflection is smaller. Stress and strain analysis of rotating material box with baffle of different thickness have been carried on. The results show that when the thickness is 20 mm or 30 mm, the value of maximum equivalent stress exceeds the allowable stress of material and the maximum deflection is too large. And when the thickness is 40 mm or 50 mm,structural strength meet the requirements. Considering the weight of the equipment, the best thickness is 40mm; The result of force analysis for improved bearing shows that the value of maximum stress and deflection are smaller, the structural strength meet the requirements.更多还原